Dog walking is an important source of physical activity and local parks are an important setting for dog walking. Park visitation characteristics of dog walkers is largely unknown. Using data from self- and proxy-report surveys completed by adults living near two parks in Melbourne, Australia in April-May 2013, this study examined the frequency and duration of park visits and intensity and duration of park-based physical activity among adults and children who visited parks with a dog compared with those who visited parks without a dog. The sample included 1187 adults (49 years, SD:13.3) and 755 children (9 years, SD:3.6). Adults (OR = 2.71, 95% CI:1.99, 3.70) and children (OR = 1.63, 95% CI:1.09, 2.44) were more likely to visit parks more frequently; adults were less likely to visit for a longer duration on weekends (OR = 0.58, 95% CI:0.43, 0.77); and children were less likely to spend more time being active (−9.22, 95% CI:−16.74, −1.70) when visiting the park with a dog versus without a dog. Adults who visited with a dog were also less likely to spend 1+ hours in the park on weekdays than <30 min (RRR = 0.53, 95% CI:0.33, 0.85) and more likely to engage in moderate than sitting/light-intensity activity (RRR = 2.30, 95% CI:1.69, 3.15). Children who visited with a dog were less likely to engage in vigorous than sitting/light-intensity activity (RRR = 0.39, 95% CI:0.16, 0.94). Adults and children who visit parks with a dog are more frequent park users therefore park access, design and amenity should support dog walkers and their engagement in physical activity.