The 29-year-old one-club man was part of the Hornets team that beat Wolves 2-1 at Vicarage Road on Saturday, with goals from Nathaniel Chalobah and Troy Deeney.
The success lifted Gianfranco Zola's side to ninth in the Championship, just a point outside the play-off positions.
"I'm very proud to get to 350 starts," Doyley said. "I've actually played more than that if you include substitute appearances but I'm just glad to be part of the club.
"I've played in most of the games this season - even if I wasn't starting - so it is good to be part of this team. We're playing well and looking up.
"Wolves have just come down from the Premier League and they made things really difficult for us. They put us under a lot of pressure, although when they had a man sent off that eased the pressure on us a little bit. It gave us more time, I think we could have put them to bed a bit easier by putting away a few more of our chances."