Previous data indicated that cats influence the moods of singly living people only by decreasing negative moods, while not affecting positive moods. In this study, we asked if such an effect can be 1) replicated, 2) is comparable to the effect of a human partner, and 3) related to the owner’s attachment towards the cat. Two hundred and twelve couples with cats, 31 couples without cats, singly living people with cats (47 women, 45 men) and singly living people without cats (43 women, 9 men) volunteered to participate. We used a list of adjectives (the “EWL”-Questionnaire) to assess their mood, which they responded to on an evening of their choice. The Lexington Attachment to Pets Scale (LAPS) was additionally completed by the cat owners. Selected adjectives were reduced by factor analyses and labeled bad mood, activity, good mood, and seclusion, according to the highest loadings of mood items within each factor. Each mood factor was explained by cat ownership, presence or absence of a partner, and the person’s sex. Further, sex, partner status and attachment towards cats explained moods amongst the cat owners. Only the partner, but not the cat, enhanced positive moods. Cats alleviated negative moods, and this effect was comparable to the effect of a human partner. This compensatory effect of cat ownership on negative moods was not comparable to a similar effect of degree of attachment towards the cat on human mood. Possible reasons for the unidirectional effect of cats on human mood are discussed.