The function of the retinitis pigmentosa GTPase regulator interacting protein 1 (RPGRIP1) gene is currently not known. However, mutations within the gene lead to Leber Congenital Amaurosis and autosomal recessive retinitis pigmentosa in human patients. In a previously described knockout mouse model of the long splice variant of Rpgrip1, herein referred to as Rpgrip1^tm1Tili mice, mislocalization of key outer segment proteins and dysmorphogenesis of outer segment discs preceded subsequent photoreceptor degeneration. In this report, we describe a new mouse model carrying a splice acceptor site mutation in Rpgrip1, herein referred to as Rpgrip1^nmf247 that is phenotypically distinct from Rpgrip1^tm1Tili mice. Photoreceptor degeneration in homozygous Rpgrip1^nmf247 mice is earlier in onset and more severe when compared with Rpgrip1^tm1Tili mice. Also, ultrastructural studies reveal that whereas Rpgrip1^nmf247 mutants have a normal structure and number of connecting cilia, unlike Rpgrip1^tm1Tili mice, they do not elaborate rod outer segments (OS). Therefore, in addition to its role in OS disc morphogenesis, RPGRIP1 is essential for rod OS formation. Our study indicates the absence of multiple Rpgrip1 isoforms in Rpgrip1^nmf247 mice, suggesting different isoforms may play different roles in photoreceptors and underscores the importance of considering splice variants when generating targeted null mutations.