| Name of the Candidate | Party Name | Results |
| SADANAND SINGH | Indian National Congress | Won 64981 |
| NIRAJ KUMAR MANDAL | Lok Jan Shakti Party | 43752 |
| PAWAN KUMAR YADAV | Independent | 26510 |
| NAJANI NAJ | Independent | 9093 |
| SANJIT SUMAN | Communist Party of India | 7339 |
| DEEPAK KUMAR | Independent | 3409 |
| SANJIV KUMAR | Communist Party of India (Marxist) | 3282 |
| PRADEEP KUMAR | Sarvajan Kalyan Loktantrik Party | 3266 |
| SUMAN KUMAR SINGH | Independent | 2757 |
| BINOD PANDEY | Independent | 2748 |
| VINDISHWRI SHARMA | National Tiger Party | 1853 |
| MANOJ KUMAR YADAV | Bahujan Samaj Party | 1726 |
| SHOBHA KANT MANDAL | Samajwadi Party | 1067 |
| None of the Above | None of the Above | 5353 |
| AC No | Category | Poll Phases | Last Date of Nominations | Date of Polls | Result |
| 155 | GEN | Phase I | Sep 23rd 2015 | Oct 12th 2015 | Nov 8th 2015 |
Kahalgaon legislative assembly segment is a part of the Bhagalpur lok sabha constituency. Kahalgaon comprises CD Blocks Goradih & Sonhoula; Gram Panchayats Parashathdih (Shankarpur Khawas), Kodwar, Janidih, Pakkisarai, Dhanora, Maishamunda, Ekchari, Bholsar, Ogree, Shyampur & Nagar Panchayat Kahalgaon of Kahalgaon CD Block.
One of the seven assembly segments located in the Bhagalpur district of Bihar, Kahalgaon is one of the only four assembly constituencies which had elected the Congress candidates in the last assembly elections in Bihar in 2010. Bahadurganj, Kishanganj and Kasba are the other three.
While Bahadurganj and Kishanganj were won by Mohammad Tausif Alam and Md Jawed respectively, the Kasba seat went in favour of Mohammad Afaq Alam. In fact, Kahalgaon is one of the very few seats in Bihar where the Congress has managed to hold its sway since earlier years of electoral politics in the state.
Former assembly speaker and ex-BPCC chief Sadanand Singh is the sitting MLA from Kahalgaon assembly seat which he won in the last general assembly polls to the Bihar Legislative assembly in 2010 by defeating his nearest rival Kahkashan Parween of the JD(U) by a margin of 8935 votes. Kahkashan Parween, a former Mayor of Bhagalpur Municipal Corporation, has been now elected to the Rajya Sabha. Shobhakant Mandal, former RJD MLA from Pirpainti, came third with 26226 votes. He did not contest the Pirpainti seat in 2010 because it was made reserved for candidates belonging to the scheduled castes.
In addition to the 2010 elections, Sadanand Singh had been elected from the Kahalgaon assembly constituency seven times. He had won the seat in 1969, 1972, 1977, 1980, 1985, 2000 and the February election in 2005. He lost to Ajay Kumar Mandal of the Janata Dal (United) in the October election in 2005. It is pertinent to note that Bihar went to the assembly polls twice in 2005 because the earlier one held in February threw hung assembly necessitating the holding of the second assembly polls in the month of November of the same year.
In 1990 and 1995, Kahalgaon assembly seat went in favour of the Janata Dal when its nominee Mahesh Prasad Mandal claimed the seat. The Janata Dal later disintegrated into several splinter groups. Communist Party Of India (CPI) managed to win the Kahalgaon assembly seat in 1967.
One of the seven assembly constituencies located in the Bhagalpur district, Kahalgaon is one of the six assembly constituencies the combination of which goes on to create the parliamentary constituency of Bhagalpur which is currently represented by Shailesh Kumar Mandal alias Bulo Mandal of the RJD who won the seat by defeating Shahnawaz Hussain of the BJP in 2014 Lok Sabha elections by a margin 9,485 votes.
Congress president Sonia Gandhi kicked off the party's campaign with a huge rally in Kahalgaon near Bhagalpur on October 3 (Saturday). This was be the first election rally of Gandhi after poll dates were announced in Bihar. After Kahalgaon, the Congress president attended another rally at Wazirganj in Gaya district on the same day. Sitting Congress MLA Sadanand Singh who has been representing the Kahalgaon constituency for several terms is in a comfortable position to win the seat. All top state party leaders of the Congress attended the Kahalgaon rally of the party. Sonia Gandhi and Rahul Gandhi were expected to address around 20 election rallies in Bihar.