There are 39 Lok Sabha seats in Tamil Nadu and one in neighbouring Puducherry, voting for all of which will be held in a single phase.
DMK president MK Stalin released the list of constituencies allotted to the allies in presence of coalition leaders, including Tamil Nadu Congress chief K S Alagiri and MDMK's Vaiko, at the party headquarters here.
Stalin also named his party-led coalition the "Secular Progressive Alliance."
Addressing a press conference, Stalin said the DMK's 20 seats include Chennai (North), Chennai (South), Chennai (Central), Tuticorin and Pollachi.
Hoping to extend its 2016 electoral success to the parliamentary polls also, the main opposition party in Tamil Nadu opted to field its candidates in 20 seats across the state including the three in Chennai where it has a sizeable number of MLAs.
Pollachi, a relatively quiet town near Coimbatore, is in the news following a sexual harassment case which has created an outrage across the state.
The DMK's other seats are: Sriperumbudur, Kancheepram (SC), Arakkonam, Vellore, Dharmapuri, Tiruvannamalai, Kallakurichi, Salem, Nilgiris (SC), Dindigul, Cuddalore, Mayiladuthurai, Thanjavur, Thenkasi (SC) and Tirunelveli.
The Congress, which has been allotted the lion's share of seats (10) among the allies, will contest from nine constituencies in Tamil Nadu, and the lone seat in Puducherry.
It will also field its nominees in Tiruvallore (SC), Krishnagiri, Karur, Theni, Virudunagar and Kanniyakumari, Sivaganga, Tiruchirappally and Arani seats, Stalin said.
The CPI(M) has been allotted Coimbatore and Madurai seats, while the CPI will fight from Tirupur and Nagapattinam, a reserved constituency.
The pro-Dalit VCK has been given Villupuram and Chidambaram, both reserved segments. The Vaiko-led MDMK has been allotted the Erode constituency.
Recalling the seat-sharing agreement with Vaiko, the DMK chief said the MDMK will also be given a Rajya Sabha seat at an appropriate time.
The Indian Union Muslim League (IUML) and the Kongunadu Makkal Desia Katchi (KMDK) will field their nominees from Ramanathapuram and Namakkal, respectively, while the India Jananayaga Katchi (IJK) has been allotted Perambalur seats, he said.
Stalin said in the last couple of years, the coalition constituents had been taking forward various protests and struggles against the "follies" of the BJP-led government at the Centre and the ruling AIADMK in Tamil Nadu.
That friendship has now transformed into an alliance, he said, adding the coalition partners came together on ideology and the partnership was not based on any 'bargain.'
He claimed that the NDA in the state, headed by his party's archrival the AIADMK, will lose the polls and that coalition led by his party will secure a "grand victory."
To a question, he said the DMK's candidate list will be announced soon.
1. Chennai North
2. Chennai South
3. Chennai Central
5. Kancheepuram (SC)
12. Nilgiris (SC)
20. Tenkasi (SC)
1. Thiruvallur (SC)
1. Villupuram (SC)
2. Chidambaram (SC)
2. Nagapattinam (SC)