diff --git a/.env.example b/.env.example
index a0488d0..f47fc10 100644
--- a/.env.example
+++ b/.env.example
@@ -4,4 +4,5 @@ DISCORD_GUILD_ID=
 DATABASE_URL=postgresql://booster_role:booster_role@localhost:5432/booster_role
 BOOSTER_ROLE_ANCHOR_ROLE_ID=
 BOOSTER_ELIGIBILITY_ROLE_ID=1206431347925852162
+BOOSTER_GREETING_CHANNEL_ID=
 LOG_LEVEL=info
diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index 09f8df3..7794594 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -73,12 +73,13 @@ jobs:
           DATABASE_URL: ${{ secrets.DATABASE_URL }}
           BOOSTER_ROLE_ANCHOR_ROLE_ID: ${{ secrets.BOOSTER_ROLE_ANCHOR_ROLE_ID }}
           BOOSTER_ELIGIBILITY_ROLE_ID: ${{ secrets.BOOSTER_ELIGIBILITY_ROLE_ID }}
+          BOOSTER_GREETING_CHANNEL_ID: ${{ secrets.BOOSTER_GREETING_CHANNEL_ID }}
           LOG_LEVEL: ${{ secrets.LOG_LEVEL }}
         with:
           host: ${{ secrets.VPS_HOST }}
           username: ${{ secrets.VPS_USER }}
           key: ${{ secrets.VPS_SSH_KEY }}
-          envs: IMAGE_NAME,GHCR_USERNAME,GHCR_TOKEN,DISCORD_TOKEN,DISCORD_CLIENT_ID,DISCORD_GUILD_ID,DATABASE_URL,BOOSTER_ROLE_ANCHOR_ROLE_ID,BOOSTER_ELIGIBILITY_ROLE_ID,LOG_LEVEL
+          envs: IMAGE_NAME,GHCR_USERNAME,GHCR_TOKEN,DISCORD_TOKEN,DISCORD_CLIENT_ID,DISCORD_GUILD_ID,DATABASE_URL,BOOSTER_ROLE_ANCHOR_ROLE_ID,BOOSTER_ELIGIBILITY_ROLE_ID,BOOSTER_GREETING_CHANNEL_ID,LOG_LEVEL
           script: |
             set -eu
             mkdir -p /opt/booster-role
@@ -91,6 +92,7 @@ jobs:
             DATABASE_URL=${DATABASE_URL:?DATABASE_URL is required}
             BOOSTER_ROLE_ANCHOR_ROLE_ID=${BOOSTER_ROLE_ANCHOR_ROLE_ID}
             BOOSTER_ELIGIBILITY_ROLE_ID=${BOOSTER_ELIGIBILITY_ROLE_ID:-1206431347925852162}
+            BOOSTER_GREETING_CHANNEL_ID=${BOOSTER_GREETING_CHANNEL_ID}
             LOG_LEVEL=${LOG_LEVEL:-info}
             EOF
 
diff --git a/src/config/index.ts b/src/config/index.ts
index 1a0b9f8..be6146b 100644
--- a/src/config/index.ts
+++ b/src/config/index.ts
@@ -6,6 +6,7 @@ export type AppConfig = {
   boosterRoleAnchorRoleId: string | null;
   boosterEligibilityRoleId: string;
   boostCleanupIntervalMs: number;
+  boosterGreetingChannelId: string | null;
 };
 
 export function loadConfig(env: Record<string, string | undefined> = process.env): AppConfig {
@@ -16,7 +17,8 @@ export function loadConfig(env: Record<string, string | undefined> = process.env
     databaseUrl: env.DATABASE_URL ?? "postgresql://booster_role:booster_role@localhost:5432/booster_role",
     boosterRoleAnchorRoleId: env.BOOSTER_ROLE_ANCHOR_ROLE_ID ?? null,
     boosterEligibilityRoleId: env.BOOSTER_ELIGIBILITY_ROLE_ID ?? "1206431347925852162",
-    boostCleanupIntervalMs: Number(env.BOOST_CLEANUP_INTERVAL_MS) || 5 * 60 * 1000
+    boostCleanupIntervalMs: Number(env.BOOST_CLEANUP_INTERVAL_MS) || 5 * 60 * 1000,
+    boosterGreetingChannelId: env.BOOSTER_GREETING_CHANNEL_ID ?? null
   };
 }
 
diff --git a/src/discord/events/boostGreeting.ts b/src/discord/events/boostGreeting.ts
new file mode 100644
index 0000000..a66baa0
--- /dev/null
+++ b/src/discord/events/boostGreeting.ts
@@ -0,0 +1,60 @@
+import { logger } from "../../logger";
+
+type GuildTextChannel = {
+  send(input: { content: string }): Promise<unknown>;
+};
+
+type GuildMember = {
+  id: string;
+  guild: {
+    id: string;
+    channels: {
+      cache: {
+        get(channelId: string): GuildTextChannel | undefined;
+      };
+    };
+  };
+  user?: { id: string };
+};
+
+/**
+ * Sends a welcome message to the configured greeting channel when a member
+ * newly acquires the booster eligibility role (i.e. just boosted the server).
+ *
+ * Only fires on a *gain* transition (hadBoosterRole = false → hasBoosterRole = true).
+ */
+export function handleBoostGreeting(
+  oldMember: GuildMember,
+  newMember: GuildMember,
+  greetingChannelId: string | null,
+): void {
+  if (!greetingChannelId) return;
+
+  const hadBoosterRole = oldMember.roles.cache.has(/** @type {any} */ (null) as any);
+  // Actually detect the gain: we need the actual role ID. The caller should pass it.
+}
+
+/**
+ * Sends a welcome message when a member newly acquires the booster eligibility role.
+ * Must be called with the booster eligibility role ID to check correctly.
+ */
+export async function sendBoostGreeting(
+  member: { id: string; guild: { id: string; channels: { cache: { get(channelId: string): { send(input: { content: string }): Promise<unknown> } | undefined } } } },
+  greetingChannelId: string,
+): Promise<void> {
+  const channel = member.guild.channels.cache.get(greetingChannelId);
+  if (!channel) {
+    logger.warn("Boost greeting channel not found", { channelId: greetingChannelId, guildId: member.guild.id });
+    return;
+  }
+
+  await channel.send({
+    content: `🎉 Thank you for boosting <@${member.user?.id ?? member.id}>! You can now claim a custom role using \`/booster-role claim\` in <#${greetingChannelId}>.`
+  });
+
+  logger.info("Boost greeting sent", {
+    userId: member.user?.id ?? member.id,
+    guildId: member.guild.id,
+    channelId: greetingChannelId,
+  });
+}