diff --git a/docker-compose.yml b/docker-compose.yml
index d643cd0..ad5fa37 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -52,8 +52,7 @@ services:
       timeout: 5s
       retries: 5
     user: postgres
-    volumes:
-      - postgres_data:/var/lib/postgresql/data
+    # postgres_data is mounted per variant: the mount point depends on the PostgreSQL image
     restart: unless-stopped
   tracker:
     build:
diff --git a/package_variants/gnosis/docker-compose.yml b/package_variants/gnosis/docker-compose.yml
index 5663547..6cfdde9 100644
--- a/package_variants/gnosis/docker-compose.yml
+++ b/package_variants/gnosis/docker-compose.yml
@@ -33,6 +33,11 @@ services:
         POSTGRES_PASSWORD: gnosis
         PGPASSWORD: gnosis
         POSTGRES_DB: web3signer-gnosis
+    # PostgreSQL 18 layout: the cluster lives in /var/lib/postgresql/18/docker inside the volume.
+    # A PostgreSQL 14 cluster from older package versions sits at the volume root and is
+    # upgraded on start by upgrade-from-14.sh.
+    volumes:
+      - postgres_data:/var/lib/postgresql
 
   tracker:
     build:
diff --git a/package_variants/hoodi/docker-compose.yml b/package_variants/hoodi/docker-compose.yml
index d33ac3e..8b578e5 100644
--- a/package_variants/hoodi/docker-compose.yml
+++ b/package_variants/hoodi/docker-compose.yml
@@ -33,6 +33,8 @@ services:
         POSTGRES_PASSWORD: password
         PGPASSWORD: password
         POSTGRES_DB: web3signer
+    volumes:
+      - postgres_data:/var/lib/postgresql/data
 
   tracker:
     build:
diff --git a/package_variants/lukso/docker-compose.yml b/package_variants/lukso/docker-compose.yml
index 72e9954..610fe12 100644
--- a/package_variants/lukso/docker-compose.yml
+++ b/package_variants/lukso/docker-compose.yml
@@ -33,6 +33,11 @@ services:
         POSTGRES_PASSWORD: password
         PGPASSWORD: password
         POSTGRES_DB: web3signer
+    # PostgreSQL 18 layout: the cluster lives in /var/lib/postgresql/18/docker inside the volume.
+    # A PostgreSQL 14 cluster from older package versions sits at the volume root and is
+    # upgraded on start by upgrade-from-14.sh.
+    volumes:
+      - postgres_data:/var/lib/postgresql
 
   tracker:
     build:
diff --git a/package_variants/mainnet/docker-compose.yml b/package_variants/mainnet/docker-compose.yml
index 833ff7c..b746bd5 100644
--- a/package_variants/mainnet/docker-compose.yml
+++ b/package_variants/mainnet/docker-compose.yml
@@ -40,6 +40,11 @@ services:
         PGPASSWORD: mainnet
         POSTGRES_DB: web3signer-mainnet
         POSTGRES_USER: postgres
+    # PostgreSQL 18 layout: the cluster lives in /var/lib/postgresql/18/docker inside the volume.
+    # A PostgreSQL 14 cluster from older package versions sits at the volume root and is
+    # upgraded on start by upgrade-from-14.sh.
+    volumes:
+      - postgres_data:/var/lib/postgresql
     
   tracker:
     build:
diff --git a/services/postgres/Dockerfile.debian b/services/postgres/Dockerfile.debian
index 37fe6d5..310067b 100644
--- a/services/postgres/Dockerfile.debian
+++ b/services/postgres/Dockerfile.debian
@@ -6,7 +6,14 @@ WORKDIR /usr/src/app
 RUN apk --no-cache add git && \
     git clone --depth 1 --branch ${WEB3SIGNER_VERSION} https://github.com/ConsenSys/web3signer.git
 
-FROM postgres:14.1-bullseye
+FROM postgres:18.6-bookworm
+
+# PostgreSQL 14 binaries are only used by upgrade-from-14.sh to dump clusters
+# created by package versions that ran PostgreSQL 14.
+RUN sed -i 's/$/ 14/' /etc/apt/sources.list.d/pgdg.list && \
+    apt-get update && \
+    apt-get install --yes --no-install-recommends postgresql-14 && \
+    rm -rf /var/lib/apt/lists/*
 
 ARG POSTGRES_PASSWORD
 ARG PGPASSWORD
@@ -22,4 +29,9 @@ ENV POSTGRES_PASSWORD=${POSTGRES_PASSWORD} \
 COPY rename_files.sh /usr/local/bin/rename_files.sh
 COPY --from=migrations-download /usr/src/app/web3signer/slashing-protection/src/main/resources/migrations/postgresql/* ${INITDB_DIR}
 
-RUN chmod +x /usr/local/bin/rename_files.sh && /usr/local/bin/rename_files.sh
\ No newline at end of file
+RUN chmod +x /usr/local/bin/rename_files.sh && /usr/local/bin/rename_files.sh
+
+COPY upgrade-from-14.sh /usr/local/bin/upgrade-from-14.sh
+
+ENTRYPOINT ["upgrade-from-14.sh"]
+CMD ["postgres"]
\ No newline at end of file
diff --git a/services/postgres/upgrade-from-14.sh b/services/postgres/upgrade-from-14.sh
new file mode 100755
index 0000000..0a4a589
--- /dev/null
+++ b/services/postgres/upgrade-from-14.sh
@@ -0,0 +1,99 @@
+#!/bin/bash
+# Entrypoint wrapper: upgrades a PostgreSQL 14 cluster created by older package versions
+# to PostgreSQL 18, then hands over to the official docker-entrypoint.sh.
+#
+# Layout (the volume is mounted at /var/lib/postgresql, as the 18+ images expect):
+#   /var/lib/postgresql/PG_VERSION = 14   -> cluster created by package versions running PostgreSQL 14
+#   /var/lib/postgresql/18/docker         -> PGDATA of the PostgreSQL 18 cluster
+#
+# Upgrade = dump/restore (the slashing protection DB is small: it is pruned to 500 epochs):
+#   1. start PostgreSQL 14 on the old cluster (unix socket only) and pg_dump every database
+#   2. initdb a PostgreSQL 18 cluster in a temporary directory and restore the dumps
+#   3. compare exact row counts of every table between both clusters
+#   4. atomically move the new cluster into PGDATA
+#   5. disable the old cluster (rename its PG_VERSION) so an older package version cannot start
+#      on it and sign with a stale slashing protection history
+# Any failure exits non-zero before step 4, leaving the old cluster untouched: postgres does not
+# start, so flyway and web3signer do not start either (fail closed). The next restart retries.
+
+set -euo pipefail
+
+OLD_DATA=/var/lib/postgresql
+OLD_BIN=/usr/lib/postgresql/14/bin
+NEW_DATA="${PGDATA}"
+WORK_DATA="${PGDATA}.upgrading"
+UPGRADE_DIR=/var/lib/postgresql/upgrade-14-to-18
+OLD_SOCKET=/tmp/pg14
+NEW_SOCKET=/tmp/pg18
+
+log() { echo "[INFO - upgrade-from-14] $*"; }
+
+# Exact row count of every user table, one "db.schema.table count" line each.
+table_counts() {
+  local bin=$1 socket=$2 db
+  for db in $("${bin}/psql" -h "${socket}" -U "${POSTGRES_USER}" -d postgres -Atc \
+    "SELECT datname FROM pg_database WHERE datallowconn AND NOT datistemplate ORDER BY 1"); do
+    "${bin}/psql" -h "${socket}" -U "${POSTGRES_USER}" -d "${db}" -At -v ON_ERROR_STOP=1 <<-SQL
+	SELECT format('SELECT %L || '' '' || count(*) FROM %I.%I', '${db}.' || schemaname || '.' || relname, schemaname, relname)
+	FROM pg_stat_user_tables ORDER BY schemaname, relname \gexec
+	SQL
+  done | sort
+}
+
+upgrade() {
+  log "Found a PostgreSQL 14 cluster in ${OLD_DATA}, upgrading it to PostgreSQL ${PG_MAJOR}"
+  rm -rf "${WORK_DATA}" "${UPGRADE_DIR}"
+  mkdir -p "$(dirname "${NEW_DATA}")" "${UPGRADE_DIR}" "${OLD_SOCKET}" "${NEW_SOCKET}"
+
+  log "Dumping databases from PostgreSQL 14"
+  "${OLD_BIN}/pg_ctl" -D "${OLD_DATA}" -w -o "-c listen_addresses='' -c unix_socket_directories=${OLD_SOCKET}" start
+  "${OLD_BIN}/psql" -h "${OLD_SOCKET}" -U "${POSTGRES_USER}" -d postgres -Atc \
+    "SELECT datname FROM pg_database WHERE datallowconn AND NOT datistemplate ORDER BY 1" > "${UPGRADE_DIR}/databases"
+  while read -r db; do
+    pg_dump -h "${OLD_SOCKET}" -U "${POSTGRES_USER}" -Fc -f "${UPGRADE_DIR}/${db}.dump" "${db}"
+  done < "${UPGRADE_DIR}/databases"
+  table_counts "${OLD_BIN}" "${OLD_SOCKET}" > "${UPGRADE_DIR}/counts-14"
+  "${OLD_BIN}/pg_ctl" -D "${OLD_DATA}" -m fast -w stop
+
+  log "Restoring into a new PostgreSQL ${PG_MAJOR} cluster"
+  initdb -D "${WORK_DATA}" --username="${POSTGRES_USER}" --pwfile=<(printf "%s\n" "${POSTGRES_PASSWORD}") > /dev/null
+  printf '\nhost all all all scram-sha-256\n' >> "${WORK_DATA}/pg_hba.conf"
+  pg_ctl -D "${WORK_DATA}" -w -o "-c listen_addresses='' -c unix_socket_directories=${NEW_SOCKET}" start
+  while read -r db; do
+    if [ "${db}" = postgres ]; then
+      pg_restore -h "${NEW_SOCKET}" -U "${POSTGRES_USER}" --exit-on-error -d postgres "${UPGRADE_DIR}/${db}.dump"
+    else
+      pg_restore -h "${NEW_SOCKET}" -U "${POSTGRES_USER}" --exit-on-error --create -d postgres "${UPGRADE_DIR}/${db}.dump"
+    fi
+  done < "${UPGRADE_DIR}/databases"
+  table_counts /usr/lib/postgresql/${PG_MAJOR}/bin "${NEW_SOCKET}" > "${UPGRADE_DIR}/counts-${PG_MAJOR}"
+  pg_ctl -D "${WORK_DATA}" -m fast -w stop
+
+  if ! diff -u "${UPGRADE_DIR}/counts-14" "${UPGRADE_DIR}/counts-${PG_MAJOR}"; then
+    echo "[ERROR - upgrade-from-14] Row counts differ between PostgreSQL 14 and ${PG_MAJOR}, aborting. The PostgreSQL 14 cluster was not modified." >&2
+    exit 1
+  fi
+  log "Row counts match: $(tr '\n' ' ' < "${UPGRADE_DIR}/counts-${PG_MAJOR}")"
+
+  mv "${WORK_DATA}" "${NEW_DATA}"
+  disable_old_cluster
+  log "Upgrade completed. Dumps kept in ${UPGRADE_DIR}"
+}
+
+disable_old_cluster() {
+  if [ -s "${OLD_DATA}/PG_VERSION" ]; then
+    mv "${OLD_DATA}/PG_VERSION" "${OLD_DATA}/PG_VERSION.upgraded-to-${PG_MAJOR}"
+    log "Disabled the old PostgreSQL 14 cluster so older package versions cannot use its stale data"
+  fi
+}
+
+if [ "${1:-}" = postgres ]; then
+  if [ -s "${NEW_DATA}/PG_VERSION" ]; then
+    # Already upgraded (or fresh install). Finish step 5 if a previous run stopped right before it.
+    disable_old_cluster
+  elif [ "$(cat "${OLD_DATA}/PG_VERSION" 2>/dev/null)" = 14 ]; then
+    upgrade
+  fi
+fi
+
+exec docker-entrypoint.sh "$@"