Sunnyside's western section, from the Humber River to west of the Bathing Pavilion is named in honour of Casimir Gzowski, a pioneer engineer in the building of railways in Canada. The park houses a monument built in the 1960s that has displays of his personal history. The park contains a children's playground and picnicking areas, a food concession stand and a stormwater catchment pond. At the western end of Gzowski Park is the Queen Elizabeth Way Monument, relocated from its location between the east and west lanes of the then Queen Elizabeth Way, which had its starting point from the Humber River. The monument was relocated to the park and rededicated by Queen Elizabeth in 1989. The park is now the site of another relocation, a Joy Oil heritage gas station from the 1930s. It has been moved from its original location north of Lake Shore Boulevard to the south side at the intersection with Ellis Avenue.

The fenced Dogs Off-Leash Area allows Commercial Dog Walkers.