Umesh had turned up for Middlesex in last year's County Championship season.
Umesh will replace New Zealand cricketer Doug Bracewell in the Essex squad. This signing makes him the second overseas player in the side, alongside Simon Harmer.
Yadav had turned up for Middlesex in last year's County Championship season. The right-arm quick hasn’t played competitive cricket since featuring in the 2023 World Test Championship (WTC) Final against Australia at The Oval in June.
Umesh will be available for Essex’s games against Middlesex, Hampshire and Northamptonshire in the County circuit.
"I am really pleased to join Essex and make what I hope will be some valuable contributions to the team's success this year."
"I enjoyed playing in England with Middlesex last season, and it will be good to return and test myself in those conditions again, especially in the midst of a title race," said Umesh via a press release.
Umesh Yadav, 35, has represented India in 57 Tests, 75 ODIs and 9 T20Is so far, claiming a total of 288 wickets across formats.
"Umesh is a superb signing for us, and we all know what he will be able to bring to our attack at a crucial time of the season," Essex head coach Anthony McGrath said.
"He is vastly experienced and has taken wickets at the top levels of the game for more than a decade now, so as well as contributing during our run-in, we hope he can pass on some of his wisdom to our young players too."