In celebration of the new couple, Park sang Only You, a song he had written for his own wife.
Also there were actor Ahn Sung Ki, who is Rain's godfather; rapper Psy; Park Joon Hyung of pop group g.o.d.; and Kim's university classmate Lee Honey.
The venue was guarded by private security guards hours, preventing a group of reporters from getting a glimpse of the couple.
Rain, 34, and Kim, 37, started dating in 2012, with news of their romance becoming public on Jan 1, 2013.
Rain and Kim Tae-hee married each other on Thursday at Gahoe-dong Cathedral in a small, private wedding.
Only family members and a few close friends including Psy and Park Jin-young, who is also known as JYP, attended the service.
Rain and Kim will unveil their wedding pictures, along with a public announcement after the wedding, Rain’s agency said Thursday.
They also have no immediate plans for a honeymoon or parenthood, according to Kim's agency.
Rain (born Jung Ji Hoon), a South Korean R&B singer and actor, has married his long time girlfriend and fellow actress Kim Tae Hee in a modest church ceremony at Gahoe-dong Cathedral in Gahoe-dong, Jongno district, Seoul on January 19.
In a wedding ceremony that lasted for about 90 minutes, Rain wore a black suit while Tae Hee looked radiant in a white dress that was above the knee.
The stars' agencies were quick to confirm the report.
Joo, 29, and Bo A, 30, both enjoy golf and mountain hiking.