Jayendra was born to Ramanathan Chettiar and Alagammai Aachi in a Nattukottai Nagarathar family in Karaikudi, Tamil Nadu.

[10] He entered his second ATP world tour event of the year at Malaysian Open where he lost in the first round to Mikhail Kukushkin.

[4] In the 2016 season, Ramanathan entered the Chennai Open and reached the quarterfinals, his best result at an ATP World Tour event.

He became the first Indian to reach an ATP World Tour singles final since Somdev Devvarman at the 2011 Johannesburg Open.

He paired with compatriot Vijay Sundar Prashanth and defeated Hsieh Cheng-peng and Yang Tsung-hua in the final.

[25] Ramanathan ended 2021 year by reaching the quarterfinals of the 2021 Antalya Challenger III in singles and the semifinals of doubles with Vladyslav Orlov.

[citation needed] Just a month later, he won his second ATP title with Rohan Bopanna at Maharashtra Open by defeating Australian pair of Luke Saville and John-Patrick Smith in the final.

[26][27] At the same tournament, Ramanathan received a singles main draw wildcard but lost to Stefano Travaglia in the first round in three sets.

[citation needed] Ramanathan lost in the first round of 2022 Bengaluru Open to Max Purcell in three sets but went on to win the doubles title with Saketh Myneni seeded no.3 defeating French pair of Hugo Grenier and Alexandre Müller in straight sets in the final.

[citation needed] He then lost to Mathias Bourgue at Bengaluru Open 2 but reached the doubles final with Saketh Myneni again losing to Arjun Kadhe and Alexander Erler in the tie breaker.

[citation needed] Ramanathan and Saketh lost in the 1st round of 2022 Dubai Tennis Championships to John Peers and Filip Polášek in straight sets after receiving a wildcard.

[citation needed] Ramanathan lost to Liam Broady in the qualifying round of 2022 Indian Wells Masters.

[citation needed] Ramanathan was the top seed in the singles qualifying round of 2022 Challenger di Roseto degli Abruzzi II but lost to Francesco Maestrelli.

He then reached the final of the Challenger Biel/Bienne with Purav Raja where they lost to top seeds Pierre-Hugues Herbert and Albano Olivetti in straight sets.

[citation needed] As the top seeds with Jeevan in doubles, he still lost to eventual champions and compatriots Yuki Bhambri and Saketh Myneni.

[citation needed] At the 2024 Rolex Shanghai Masters he qualified for the main draw with wins over Ugo Blanchet and Fajing Sun.

It was his first singles main draw appearance at the Masters level since 2017 Cincinnati, having entered the qualifying competition as an alternate.