Seinfeld Season 1 cast ages
How old were Seinfeld actors in Season 1?
Jerry Seinfeld was 35, Julia Louis-Dreyfus was 28, Jason Alexander was 29 years old on 1989-07-05, the Season 1 premiere date.
These are actors’ ages on the original broadcast date, not their characters’ ages or ages during filming. This is a selected series cast comparison, not a verified list of appearances in “Good News, Bad News”. Elaine does not appear in the 1989 pilot; Julia Louis-Dreyfus joined the regular run in 1990.
Selected cast ages on 1989-07-05
| Actor | Character | Birthday | Age on air date |
|---|---|---|---|
| Jerry Seinfeld | Jerry Seinfeld | 1954-04-29 | 35 years |
| Julia Louis-Dreyfus | Elaine Benes | 1961-01-13 | 28 years |
| Jason Alexander | George Costanza | 1959-09-23 | 29 years |
| Michael Richards | Cosmo Kramer | 1949-07-24 | 39 years |
Selected actor ages by episode in Season 1
Compare completed birthdays across this season’s original air dates. Episode links select that broadcast in the explorer. These comparisons do not assert that each actor appeared in every episode.
| Episode | Air date / source | Jerry Seinfeld | Julia Louis-Dreyfus | Jason Alexander |
|---|---|---|---|---|
| Episode 1: The Seinfeld Chronicles | 1989-07-05 | 35 | 28 | 29 |
| Episode 2: The Stake Out | 1990-05-31 | 36 | 29 | 30 |
| Episode 3: The Robbery | 1990-06-07 | 36 | 29 | 30 |
| Episode 4: Male Unbonding | 1990-06-14 | 36 | 29 | 30 |
| Episode 5: The Stock Tip | 1990-06-21 | 36 | 29 | 30 |
All Seinfeld seasons and cast ages
How these ages are calculated
Subtract the actor’s birth year from the air-date year, then subtract one if their birthday had not yet occurred. Tables and the episode explorer use completed years. Missing, invalid, conflicting or unchecked birthdays do not produce an exact age. Historical broadcast ages do not imply that an actor is still living.
Premiere dates and matched birthdays were cross-checked against TVmaze’s Seinfeld guide on 2026-10-16. Actor-name links identify birthday sources; premiere-date links identify episode sources. TVmaze data is used under CC BY-SA. A database match is not independent biographical authentication; unresolved disagreements are withheld. Episode rosters and guest credits remain under review.