Homozygous Groggy dams, which carry a Cacna1a missense mutation, often show no interest in their offspring, leading to frequent offspring deaths due to lack of nurturing. The present study aimed to clarify whether the Cacna1a mutation contributes to impaired attachment behaviors between dam and offspring. The open field test showed that homozygous female rats exhibited markedly short travel distance, whereas no difference was found between the motor activity of heterozygous females and that of wild types (WT). A series of behavioral tests was performed to compare the mother–offspring relationship between WT and heterozygous rats. Performance in the pup retrieval test was significantly less successful in heterozygous than WT dams. During the experiment, heterozygous dams spent significantly less time licking and crouching than WT dams. The offspring dam-seeking behavior test revealed that heterozygous pups’ vocalizations were significantly less frequent and shorter than those of WT pups. Although no significant difference was found between WT and heterozygous offspring in the olfactory sense test, using a piece of chocolate, heterozygous pups took significantly longer to reach a sample of the dam’s bedding. Taken together, these findings suggest that the Cacna1a mutation impairs both the dam’s maternal behavior and the offspring’s attachment behavior toward the dam.