This all depends on how accepting your kitty is of your new pup. Some pairings will take only days, and in some cases (although rare), they will never get along. That said, it usually takes the two pets around two to three weeks to get acquainted. In truth, you never know how cats and dogs are going to react to one another. But with these tips and need-to-knows, you’ll be on the right track to giving these two a chance to live together peacefully.