diff --git a/beacon_node/beacon_chain/src/beacon_chain.rs b/beacon_node/beacon_chain/src/beacon_chain.rs
index e226c707a4..6d316e3271 100644
--- a/beacon_node/beacon_chain/src/beacon_chain.rs
+++ b/beacon_node/beacon_chain/src/beacon_chain.rs
@@ -1941,6 +1941,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         let beacon_block_root;
         let beacon_state_root;
         let target;
+        let is_attesting_to_head_slot;
         let current_epoch_attesting_info: Option<(Checkpoint, usize)>;
         let head_timer = metrics::start_timer(&metrics::ATTESTATION_PRODUCTION_HEAD_SCRAPE_SECONDS);
         let head_span = debug_span!("attestation_production_head_scrape").entered();
@@ -1977,7 +1978,8 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                 });
             }
 
-            if request_slot >= head_state.slot() {
+            is_attesting_to_head_slot = request_slot >= head_state.slot();
+            if is_attesting_to_head_slot {
                 // When attesting to the head slot or later, always use the head of the chain.
                 beacon_block_root = head.beacon_block_root;
                 beacon_state_root = head.beacon_state_root();
@@ -2080,6 +2082,26 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                 )
             };
 
+        // TODO(gloas): add integration test: verify that
+        // `produce_unaggregated_attestation` sets index=1 when payload received for a prior
+        // slot, index=0 for same-slot, and index=0 when payload not received.
+        //
+        // For gloas the attestation data index indicates payload presence:
+        // `payload_present=false` for same-slot attestations or when payload not received.
+        // `payload_present=true` when attesting to a prior slot whose payload has been received.
+        let payload_present = if self
+            .spec
+            .fork_name_at_slot::<T::EthSpec>(request_slot)
+            .gloas_enabled()
+            && !is_attesting_to_head_slot
+        {
+            self.canonical_head
+                .fork_choice_read_lock()
+                .is_payload_received(&beacon_block_root)
+        } else {
+            false
+        };
+
         Ok(Attestation::<T::EthSpec>::empty_for_signing(
             request_index,
             committee_len,
@@ -2087,6 +2109,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             beacon_block_root,
             justified_checkpoint,
             target,
+            payload_present,
             &self.spec,
         )?)
     }
diff --git a/beacon_node/beacon_chain/src/early_attester_cache.rs b/beacon_node/beacon_chain/src/early_attester_cache.rs
index 752e4d1a96..5b55c8e2da 100644
--- a/beacon_node/beacon_chain/src/early_attester_cache.rs
+++ b/beacon_node/beacon_chain/src/early_attester_cache.rs
@@ -204,6 +204,7 @@ impl<E: EthSpec> EarlyAttesterCache<E> {
             item.beacon_block_root,
             item.source,
             item.target,
+            false,
             spec,
         )
         .map_err(Error::AttestationError)?;
diff --git a/beacon_node/beacon_chain/src/test_utils.rs b/beacon_node/beacon_chain/src/test_utils.rs
index 13dcf22108..baff1424ba 100644
--- a/beacon_node/beacon_chain/src/test_utils.rs
+++ b/beacon_node/beacon_chain/src/test_utils.rs
@@ -1400,6 +1400,7 @@ where
                 epoch,
                 root: target_root,
             },
+            false,
             &self.spec,
         )?;
 
@@ -1509,6 +1510,7 @@ where
                 epoch,
                 root: target_root,
             },
+            false,
             &self.spec,
         )?)
     }
diff --git a/consensus/fork_choice/src/fork_choice.rs b/consensus/fork_choice/src/fork_choice.rs
index 92fd4c1faf..6c1a79f820 100644
--- a/consensus/fork_choice/src/fork_choice.rs
+++ b/consensus/fork_choice/src/fork_choice.rs
@@ -1484,6 +1484,11 @@ where
             && self.is_finalized_checkpoint_or_descendant(*block_root)
     }
 
+    /// Returns `true` if the block's execution payload envelope has been received.
+    pub fn is_payload_received(&self, block_root: &Hash256) -> bool {
+        self.proto_array.is_payload_received(block_root)
+    }
+
     /// Returns a `ProtoBlock` if the block is known **and** a descendant of the finalized root.
     pub fn get_block(&self, block_root: &Hash256) -> Option<ProtoBlock> {
         if self.is_finalized_checkpoint_or_descendant(*block_root) {
diff --git a/consensus/types/src/attestation/attestation.rs b/consensus/types/src/attestation/attestation.rs
index 693b5889f5..5131be4424 100644
--- a/consensus/types/src/attestation/attestation.rs
+++ b/consensus/types/src/attestation/attestation.rs
@@ -109,6 +109,7 @@ impl<E: EthSpec> Attestation<E> {
         beacon_block_root: Hash256,
         source: Checkpoint,
         target: Checkpoint,
+        payload_present: bool,
         spec: &ChainSpec,
     ) -> Result<Self, Error> {
         if spec.fork_name_at_slot::<E>(slot).electra_enabled() {
@@ -116,12 +117,19 @@ impl<E: EthSpec> Attestation<E> {
             committee_bits
                 .set(committee_index as usize, true)
                 .map_err(|_| Error::InvalidCommitteeIndex)?;
+            // Gloas attestation data index now indicates payload presence.
+            // Pre-gloas index is always 0.
+            let index = if spec.fork_name_at_slot::<E>(slot).gloas_enabled() && payload_present {
+                1u64
+            } else {
+                0u64
+            };
             Ok(Attestation::Electra(AttestationElectra {
                 aggregation_bits: BitList::with_capacity(committee_length)
                     .map_err(|_| Error::InvalidCommitteeLength)?,
                 data: AttestationData {
                     slot,
-                    index: 0u64,
+                    index,
                     beacon_block_root,
                     source,
                     target,
diff --git a/validator_client/validator_services/src/attestation_service.rs b/validator_client/validator_services/src/attestation_service.rs
index fe808efd88..de55422f49 100644
--- a/validator_client/validator_services/src/attestation_service.rs
+++ b/validator_client/validator_services/src/attestation_service.rs
@@ -546,6 +546,7 @@ impl<S: ValidatorStore + 'static, T: SlotClock + 'static> AttestationService<S,
                 attestation_data.beacon_block_root,
                 attestation_data.source,
                 attestation_data.target,
+                attestation_data.index != 0,
                 &self.chain_spec,
             ) {
                 Ok(attestation) => attestation,