Companion dogs are at risk of tick infestations. This paper describes cases of transfer of Dermacentor reticulatus ticks by dogs to apartments in eastern Poland, tick development in household conditions, and potential consequences for the residents. For the first time, the preoviposition and oviposition of D. reticulatus females removed from dogs or spontaneously detached from these hosts were studied in household conditions. Similar analyses were performed simultaneously in laboratory settings (25 °C and 75% RH). In the household characterized by a temperature range of 18.5–21.3 °C and 46.9–56% humidity, the preoviposition and oviposition periods with the development of D. reticulatus larvae lasted 20.8 ± 3.1 days and 29.9 ± 1.4 days, respectively. Greater numbers of eggs (2415.8 ± 983.1) were laid by females in the household than laboratory conditions. There were no statistically significant differences in the hatching success between both experiments. The study also provides the first description of infestation of a human by a partially engorged D. reticulatus female that had detached from dog’s skin. Ticks transferred by dogs can develop successfully in human homes. After feeding on dogs, females achieve high reproductive performance. This suggests that dogs may play an important role in the biology of this tick species in urbanized areas.