The BJP won the by-election from the Nepanagar assembly constituency in Madhya Pradesh and was leading in the Shahdol Lok Sabha seat, officials said.
Bharatiya Janata Party's Manju Dadu won from Nepanagar by 42,198 votes, defeating Antar Singh of the Congress.
Chief Minister Shivraj Singh Chouhan expressed gratitude to the voters for the BJP's victory.
In Shahdol, where 17 candidates were in the fray, BJP's Gyan Singh led over Himandri Singh of the Congress by 26,089 votes.
The by-polls were held on Saturday. Shadol and Nepanagar registered 66 per cent and 73 per cent voting respectively.
BJP leader Sushma Swaraj, set to win from Vidisha in Madhya Pradesh, Friday attributed the thumping victory of the party in the Lok Sabha election to the hard work of the millions of BJP workers and the "able leadership of Narendra Modi".
Sushma Swaraj, who is said to be no Modi camp follower, in a tweet said: "This victory is the result of hard labour of millions of BJP 'karyakartas', blessings of (Rashtriya Swayamsewak) Sangh and able leadership of Narendra Modi."
The opposition Congress was in the second spot, leading in 74 seats. The Bahujan Samaj Party tally stood at five seats and others were six.
The BJP's prime ministerial candidate Narendra Modi was quick to hail Chief Minister Shivraj Singh Chouhan, who now gets to continue in office for a third consecutive term.
"Called Shivraj ji to congratulate him for BJP's wonderful performance in the Madhya Pradesh Parliament Elections!," tweeted Modi after the BJP headed to a thumping victory in Madhya Pradesh.
Chouhan, 53, was first appointed chief minister in 2005. Before that, the BJP's Uma Bharati became the chief minister in 2003 and after she quit, Babulal Gaur became the chief minister for a short while.
"The chief minister, Shivraj Singh Chouhan, is heading for the hat-trick in the state," said state BJP leader Narendra Singh Tomar.
The vote count started across 51 districts at 8 a.m. Postal ballots were counted first and half an hour later, the counting of ballots cast through the electronic voting machines (EVMs) began.
As many as 2,583 candidates battled it out in the election for which polling took place Nov 25.
The electoral battle was primarily between the ruling Bharatiya Janata Party and the Congress, with the BJP trouncing the latter.
As the results began to pour in, the BJP workers began celebrating across the sprawling state.
They fire crackers, beat drums, distributed sweets and waved their party flag, celebrating the poll success.
In the last assembly, the BJP had 143 members and the Congress 71. The voting percentage this time was 70 percent of the total electorate of 4,64,57,724.
Andhrapradesh Elections | Arunachalpradesh Elections | Assam Elections | Bihar Elections | Chattisgarh Elections | Delhi Elections | Goa Election News | Gujarat Election Results | Haryana Elections | Himachal Pradesh Elections | Jammu And Kashmir Elections | Jharkhand Elections | Karnataka Elections | Kerala Elections | Madhya Pradesh Elections | Maharashtra Elections | Manipur Elections | Meghalaya Elections | Mizoram Elections | Nagaland Elections | Orissa Elections | Pondicherry Elections | Punjab Elections | Rajasthan Elections | Sikkim Elections | Tamil Nadu Elections | Tripura Elections | Uttaranchal Elections | Uttarakhand Elections | U.P. Elections | West Bengal Elections | Election News