The Mercer Island Lacrosse Club was founded in 1993, when it managed boys' lacrosse teams at the high school level. In 2010, in addition to three high school teams, the club manages 12 teams covering boys in first grade through middle school, including a select team of 7th and 8th graders called the Black Team. The club oversees season league play, fall ball play and summer camps. The club is governed by a volunteer board, with Ian O'Hearn serving as Program Manager, as well as the high school varsity coach. Since 2002 when O'Hearn joined the program, the club has expanded from four teams to 15. During spring break, varsity high school players travel to New York to seek out the best competition in the country. Also in the spring, the club hosts the Northwest Invitational Tournament, which has drawn high-level teams from Canada, Oregon, Texas and New York. The club relies on fundraisers which include the well-known Christmas tree pickup/recycling program, and the annual sale of holiday poinsettias and wreaths.
The Mercer Island Beach Club is located on 625 feet of waterfront at the south end of Mercer Island. Once the site of the Seattle Central Lions Club summer camp, this family oriented member-owned club has been active since 1953. The grounds include two swimming pools (an eight lane competition pool and an activity pool with a lazy river), six outdoor tennis courts, a fitness center, outdoor pickle-ball, basketball and volleyball courts, a sandy beach, a lake roped off swimming area with dock and waterslide, a play structure, boat moorage, a firepit and a barbeque area with many picnic tables.
Summer adult tennis programs include Ladies Night, Mens Night, Saturday morning Wimbledon workout and Cardio tennis. The year round fitness center offers a variety of classes - Boot Camp, Abs, Buns, & Guns, Tone Body Basic, Teen Training, Yoga and Personal Training. Group and private swim lessons are available through the aquatics program. MIBC junior teams compete in the popular summer Midlakes swim, dive and water polo leagues. Junior tennis players participate in the summer Junior Eastside Tennis (JET) league. The pool is covered during the fall, winter and spring months, making swimming accessible year round. Social programs are held throughout the year - Family 4th of July Celebration, Songs & S'mores and Dive In Movie Night are popular summer events. A large clubhouse with expansive views of Mt Rainier and Lake Washington is available for club functions and private rentals.
The Veterans of Foreign Wars Post 5760 is Mercer Island's principal military veterans organization.
More than 70 members participate in the club, which supports companionship and service to the local community. Some of the programs and events the club supports includes a Relief Fund for veterans needing medical or material support, hospital visits and Summer Celebration.
The VFW's home, Keewaydin Clubhouse, is itself an institution. Originally built as Mercer Island's first community hall in 1922, the building recently saw a number of repairs and refurbishment. It is available for rental for special events and community functions. The VFW purchased the hall in 1966.
The Mercer Island Saddle Club is a cooperative non-profit club supported by the volunteer work of its members. Located on the south end of Mercer Island, the Saddle Club houses a 20-horse barn, a large outdoor arena, a covered arena, a hot water wash rack and two turnout paddocks. Members can board their horse, lease a horse and take riding lessons with independent trainers. The southeast quadrant of Pioneer Park, directly east of the MISC, provides 40 acres of equestrian trails for riders.