Causatives have received considerable attention in first language acquisition. Of Mayan languages, acquisition of the causative has only been investigated for K'iche' and Tzotzil, based on longitudinal and spontaneous data. K'iche'-speaking children do not acquire morphological causatives until the age of 3 years, while children acquiring Tzotzil start producing morphological causatives around the age of 2 years. The marked difference in the age of acquisition of causatives in K'iche' and in Tzotzil has been explained through a morphological difference between causatives in the two languages. This paper, based on longitudinal and spontaneous data, examines acquisition of the causative in Q'anjob'al, a third Mayan language. The question is whether the findings in K'iche' and Tzotzil are reproduced, or whether the acquisition of Q'anjob'al causatives follows a third, yet-unattested, trajectory. The results show that three Q'anjob'al children, of the age range 1;9-3;0, 2;3-4;0, and 2;7-3;6, acquire the morphological and periphrastic causatives during the third year of life, although these children produce more periphrastic causatives than morphological causatives. Longitudinal and spontaneous studies in K'iche' and Tzotzil have reported the acquisition of the morphological causative, but not the acquisition of periphrastic causatives. The Q'anjob'al children's production of more periphrastic causatives might be due to their exposure to a special V1V2 construction, which is a general feature of Q'anjob'al. The Q'anjob'al child data show that even related languages in which causatives are expressed through similar morphemes can show strikingly different acquisition trajectories.