Rajender Reddy, TDP legislator from Narayan Peth in Mahabubnagar district, said he decided to quit the party in the interest of his constituency's development.
The MLA regretted he could not do much for his Assembly segment's development in the last 20 months.
Reddy said he would hold talks with TRS President and Chief Minister K Chandrasekhar Rao after he returns here from Delhi.
Reddy, speaking at a TDP meeting presided over by party boss and Andhra Pradesh Chief Minister Chandrababu Naidu earlier in the day, expressed anguish over the outfit's affairs in Telangana in the wake of electoral defeats and desertions from its ranks.
If Reddy also joins TRS, the number of TDP MLAs who have switched over to the ruling party since 2014 would rise to 10. The Naidu-led outfit had won 15 seats in the 2014 Assembly elections.