diff --git a/.github/actions/spelling/expect.txt b/.github/actions/spelling/expect.txt
index 458168dd4cf11..bfb73adbbca43 100644
--- a/.github/actions/spelling/expect.txt
+++ b/.github/actions/spelling/expect.txt
@@ -852,7 +852,6 @@ presetdir
 pretrunc
 prettydiff
 primaryfont
-probot
 processname
 procid
 promhttp
@@ -1051,6 +1050,7 @@ subfolders
 subfooter
 sublimelinter
 subsec
+subsecond
 substrategies
 subtagline
 subtimer
diff --git a/Cargo.lock b/Cargo.lock
index 5259d73832987..d6f1ff51d6c3c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2194,6 +2194,7 @@ dependencies = [
  "rstest",
  "serde",
  "serde_json",
+ "serde_with 3.11.0",
  "similar-asserts",
  "smallvec",
  "snafu 0.7.5",
diff --git a/changelog.d/gelf-timestamp-nanoseconds.fix.md b/changelog.d/gelf-timestamp-nanoseconds.fix.md
new file mode 100644
index 0000000000000..1b4e2ddb1e5e8
--- /dev/null
+++ b/changelog.d/gelf-timestamp-nanoseconds.fix.md
@@ -0,0 +1,4 @@
+The `gelf` codec now correctly deserializes the subsecond portion of timestamps rather than dropping
+them.
+
+authors: jszwedko
diff --git a/lib/codecs/Cargo.toml b/lib/codecs/Cargo.toml
index 691e2fd91c675..1791dab4fa8fa 100644
--- a/lib/codecs/Cargo.toml
+++ b/lib/codecs/Cargo.toml
@@ -24,6 +24,7 @@ prost.workspace = true
 prost-reflect.workspace = true
 regex = { version = "1.11.0", default-features = false, features = ["std", "perf"] }
 serde.workspace = true
+serde_with = { version = "3.11.0", default-features = false, features = ["std", "macros", "chrono_0_4"] }
 serde_json.workspace = true
 smallvec = { version = "1", default-features = false, features = ["union"] }
 snafu = { version = "0.7.5", default-features = false, features = ["futures"] }
diff --git a/lib/codecs/src/decoding/format/gelf.rs b/lib/codecs/src/decoding/format/gelf.rs
index 66613cee9c679..c37924072ffa6 100644
--- a/lib/codecs/src/decoding/format/gelf.rs
+++ b/lib/codecs/src/decoding/format/gelf.rs
@@ -3,6 +3,7 @@ use chrono::{DateTime, Utc};
 use derivative::Derivative;
 use lookup::{event_path, owned_value_path};
 use serde::{Deserialize, Serialize};
+use serde_with::{serde_as, TimestampSecondsWithFrac};
 use smallvec::{smallvec, SmallVec};
 use std::collections::HashMap;
 use vector_config::configurable_component;
@@ -133,12 +134,7 @@ impl GelfDeserializer {
 
         if let Some(timestamp_key) = log_schema().timestamp_key_target_path() {
             if let Some(timestamp) = parsed.timestamp {
-                let dt = DateTime::from_timestamp(
-                    f64::trunc(timestamp) as i64,
-                    f64::fract(timestamp) as u32,
-                )
-                .expect("invalid timestamp");
-                log.insert(timestamp_key, dt);
+                log.insert(timestamp_key, timestamp);
                 // per GELF spec- add timestamp if not provided
             } else {
                 log.insert(timestamp_key, Utc::now());
@@ -204,13 +200,15 @@ impl GelfDeserializer {
     }
 }
 
+#[serde_as]
 #[derive(Serialize, Deserialize, Debug)]
 struct GelfMessage {
     version: String,
     host: String,
     short_message: String,
     full_message: Option<String>,
-    timestamp: Option<f64>,
+    #[serde_as(as = "Option<TimestampSecondsWithFrac<f64>>")]
+    timestamp: Option<DateTime<Utc>>,
     level: Option<u8>,
     facility: Option<String>,
     line: Option<f64>,
@@ -301,8 +299,7 @@ mod tests {
                 b"Backtrace here\n\nmore stuff"
             )))
         );
-        // Vector does not use the nanos
-        let dt = DateTime::from_timestamp(1385053862, 0).expect("invalid timestamp");
+        let dt = DateTime::from_timestamp(1385053862, 307_200_000).expect("invalid timestamp");
         assert_eq!(log.get(TIMESTAMP), Some(&Value::Timestamp(dt)));
         assert_eq!(log.get(LEVEL), Some(&Value::Integer(1)));
         assert_eq!(