The ruling Socialist party of Bulgarian Prime Minister Sergey Stanishev placed second and the ethnic Turkish party DPS was third, said Biser Troyanov, spokesman for the central election commission.
Despite its comfortable victory of 39.7 percent, Borisov's party will have to pull together a coalition to form a new government to replace Stanishev's Socialist-led coalition.
With 100 percent of ballots counted, the Socialists won 17.7 percent and the ethnic Turkish DPS party won 14.4 percent, Troyanov told the Bulgarian news agency SNA.
Stanishev congratulated Borisov on his victory in the elections Sunday when 6.8 million voters were eligible to elect 240 members of the Bulgarian Parliament.
The GERB party of populist Borisov, whose former occupation included those of a firefighter, bodyguard, and police chief, early in June won Bulgarian elections for the European Parliament.
Borisov has become one of the country's most popular personalities with his statements promising he will solve organized crime and corruption that have been hurting Bulgaria in the past 20 years.
Bulgaria became a member of the European Union in January 2007 but since then $700 million in EU funds have been frozen, waiting for the Sofia government to intensify the struggle against corruption and organized crime.