Visual acuity is the ability to distinguish details and this ability differs between animals. Humans have a high visual acuity in daylight intensities and dogs have been suggested to have about three to four times poorer visual acuity in daylight intensities than humans. However, dogs have eyes that are adapted to dim light conditions, which raises the question if dogs have better visual acuity in dim light. In this study a two-alternative choice test was used to behaviourally test the visual acuity in three dogs and eight humans in both daylight and dim light conditions. In daylight dogs were able to discriminate up to 12 cycle per degree (CPD), while humans could discriminate 64 CPD. In dim light dogs were able to discriminate up to 2 CPD, while humans could discriminate up to 10 CPD. Hence, humans were found to have better visual acuity in both daylight and dim light intensities.