In 1921, a football section was established at the Volunteer Fire Department in Żelechów. Its founders were Antoni Gronkiewicz and Henryk Bronicki. The section included both members of the fire brigade and others who simply wanted to play the game. It was easy to get costumes and balls, but proper football boots were hard to come by. The biggest difficulty was the lack of a suitable field to play on. Therefore, games were played on the narrow, sandy and uneven town square. The goals were makeshift and the crossbars were represented by a rope. Matches were played against teams from neighboring towns, traveling by horse-drawn wagons for away games. The team's base was the fire station where equipment was stored and the team had its changing room.

Gradually, football began to gain more supporters and enthusiasts. The entire youth played it and even schoolchildren started kicking the ball. A Jewish team was formed, which began to compete with the fire brigade team for primacy in the city. These matches were played in a turbulent atmosphere, as certain groups used them as an opportunity for anti-Semitic incidents. In 1930, during such a match, the son of the police commander was injured. This became a pretext for embarrassing incidents, the echo of which reached the county authorities. As a result, the field was closed, or more precisely, playing football matches in Żelechów was forbidden. This was the beginning of the development of other sports - volleyball, basketball, athletics, and cycling. They were popularized by the local branch of the Rifle Association. In the following years, an artificial pool was built on Wilczyska Street, which served as a municipal swimming pool in the summer and an ice rink in the winter. The land chosen during the construction of the pool was used to build a shooting range. A wooden toboggan run was built near these facilities. In this way, in the over-eight-thousand-people Żelechów, both competitive and recreational sports existed.

In 1934, a football team was reorganized and named the "Sęp" Sports Club. In the same year, a Jewish team called "Hapoel" was established. The first presidents of "Sęp" were Stanisław Zwoliński, Bolesław Domański and Tadeusz Szuster. From 1934 to 1936, "Sęp" played on two makeshift fields in the Żelechów estate, on the so-called "okólnik" and on the meadows. In 1937, the games were played opposite the coat of arms of today's City Hall, in the place of the current "Przychodnia" Health Center. From 1938 to 1939, they played on their own field behind the shooting range on Wilczyska Street. The club's dynamic activity was interrupted by the outbreak of World War II.

During football matches in Żelechów, an interesting phenomenon was the performances of the local brass band, which entertained the audience while waiting for the games and during the break, effectively combining the promotion of musical culture with physical culture.

In 1947, the team was reactivated. In 1949, the sports club was named "Włókniarz", and a year later "Związkowiec". From 1950 to 1957, it operated under the name "Start". The club was represented in the following sections: football, women's and men's volleyball, table tennis, ice hockey, and athletics. From 1958, it was named "Żelechowianka". The following year, "Żelechowianka" ceased to exist. The main reason for this was the lack of a football field. The area where the previous football field was located was designated for the construction of a comprehensive high school.

After the club was dissolved, teachers from schools took over sports and educational activities among young people. During this period, the following disciplines still existed: cycling, women's and men's volleyball, ice hockey, handball, and table tennis. There was also a significant development of sports acrobatics, and wrestling and motor sections were active.

In the 1960s, the People's Sports Club was established, which was given the name "Sęp" to maintain the old traditions. In 1967, a new football field was opened at the Vocational School Complex. In the following years, arduous but consistent efforts were made to rebuild football in Żelechów. Dr. Kazimierz Bacia, a longtime club president, made a huge contribution to these efforts. The 1980s were the culmination of these efforts. In the 1982/1983 season, "Sęp" achieved its greatest success by participating in the III league competition.

Currently, the "Sęp" team plays in the Mazovian District League in the Siedlce group. The players wear white and blue jerseys. Since 2000, the club has had a stadium with lighting and grandstands for 180 people on Chłopickiego Street. "Sęp" Żelechów is the oldest among all currently operating football clubs in the Garwolin district and even in the entire Siedlce region. The team has had players such as Janusz Białek and Marek Parzyszek.