diff --git a/lcli/src/indexed_attestations.rs b/lcli/src/indexed_attestations.rs
new file mode 100644
index 0000000000..6e3bfa51d3
--- /dev/null
+++ b/lcli/src/indexed_attestations.rs
@@ -0,0 +1,48 @@
+use clap::ArgMatches;
+use clap_utils::parse_required;
+use state_processing::common::get_indexed_attestation;
+use std::fs::File;
+use std::io::Read;
+use std::path::{Path, PathBuf};
+use types::*;
+
+fn read_file_bytes(filename: &Path) -> Result<Vec<u8>, String> {
+    let mut bytes = vec![];
+    let mut file = File::open(filename)
+        .map_err(|e| format!("Unable to open {}: {}", filename.display(), e))?;
+    file.read_to_end(&mut bytes)
+        .map_err(|e| format!("Unable to read {}: {}", filename.display(), e))?;
+    Ok(bytes)
+}
+
+pub fn run<T: EthSpec>(matches: &ArgMatches) -> Result<(), String> {
+    let spec = &T::default_spec();
+
+    let state_file: PathBuf = parse_required(matches, "state")?;
+    let attestations_file: PathBuf = parse_required(matches, "attestations")?;
+
+    let mut state = BeaconState::<T>::from_ssz_bytes(&read_file_bytes(&state_file)?, spec)
+        .map_err(|e| format!("Invalid state: {:?}", e))?;
+    state
+        .build_all_committee_caches(spec)
+        .map_err(|e| format!("{:?}", e))?;
+
+    let attestations: Vec<Attestation<T>> =
+        serde_json::from_slice(&read_file_bytes(&attestations_file)?)
+            .map_err(|e| format!("Invalid attestation list: {:?}", e))?;
+
+    let indexed_attestations = attestations
+        .into_iter()
+        .map(|att| {
+            let committee = state.get_beacon_committee(att.data.slot, att.data.index)?;
+            get_indexed_attestation(committee.committee, &att)
+        })
+        .collect::<Result<Vec<_>, _>>()
+        .map_err(|e| format!("Error constructing indexed attestation: {:?}", e))?;
+
+    let string_output = serde_json::to_string_pretty(&indexed_attestations)
+        .map_err(|e| format!("Unable to convert to JSON: {:?}", e))?;
+    println!("{}", string_output);
+
+    Ok(())
+}
diff --git a/lcli/src/main.rs b/lcli/src/main.rs
index 996bfc0ac7..0a36768d15 100644
--- a/lcli/src/main.rs
+++ b/lcli/src/main.rs
@@ -6,6 +6,7 @@ mod create_payload_header;
 mod deploy_deposit_contract;
 mod eth1_genesis;
 mod generate_bootnode_enr;
+mod indexed_attestations;
 mod insecure_validators;
 mod interop_genesis;
 mod new_testnet;
@@ -598,6 +599,26 @@ fn main() {
                         .help("The number of nodes to divide the validator keys to"),
                 )
         )
+        .subcommand(
+            SubCommand::with_name("indexed-attestations")
+                .about("Convert attestations to indexed form, using the committees from a state.")
+                .arg(
+                    Arg::with_name("state")
+                        .long("state")
+                        .value_name("SSZ_STATE")
+                        .takes_value(true)
+                        .required(true)
+                        .help("BeaconState to generate committees from (SSZ)"),
+                )
+                .arg(
+                    Arg::with_name("attestations")
+                        .long("attestations")
+                        .value_name("JSON_ATTESTATIONS")
+                        .takes_value(true)
+                        .required(true)
+                        .help("List of Attestations to convert to indexed form (JSON)"),
+                )
+        )
         .get_matches();
 
     let result = matches
@@ -679,6 +700,8 @@ fn run<T: EthSpec>(
             .map_err(|e| format!("Failed to run generate-bootnode-enr command: {}", e)),
         ("insecure-validators", Some(matches)) => insecure_validators::run(matches)
             .map_err(|e| format!("Failed to run insecure-validators command: {}", e)),
+        ("indexed-attestations", Some(matches)) => indexed_attestations::run::<T>(matches)
+            .map_err(|e| format!("Failed to run indexed-attestations command: {}", e)),
         (other, _) => Err(format!("Unknown subcommand {}. See --help.", other)),
     }
 }