Research on psychotherapy has found that characteristics of clients and therapists often are more strongly associated with treatment outcome than are specific therapeutic models or techniques. This study examined the relations between client and therapist common factors and outcomes of couple therapy. The sample was 40 couples presenting with mild to moderate psychological and physical abuse and who received ten sessions of couple therapy at a university-based clinic. The study investigated relations of client common factor characteristics (negative communication and negative attributions) and the therapist common factor characteristics (warmth, empathy, presence, validation and systemic techniques and session structuring) with couple therapy outcomes (changes in overall relationship satisfaction and in level of psychologically abusive behavior). Hierarchical linear modeling analyses testing an Actor-Partner Interdependence Model (APIM) revealed that males' negative attributions were associated with a decrease over treatment in their own use of psychological abuse, whereas females' negative attributions were associated with increased use of psychological abuse by males. Females' negative communication was associated with increased psychological abuse by females. As expected, therapist use of technique factors was associated with decreased psychological abuse by males. Unexpectedly, therapist presence was associated with less positive change in relationship satisfaction for males, and therapist use of technique factors was associated with less positive change in relationship satisfaction and increased use of psychological abuse for females. Therapist factors moderated the relationships between the client pre-treatment negative characteristics and therapy outcome, such that in some cases higher levels of therapist factors (warmth, presence, validation) enhanced a positive relationship between pre-treatment negativity and positive therapeutic outcomes and in others higher levels of the therapist factors (technique factors, presence, validation) amplified a negative relationship between pre-treatment characteristics and poor therapeutic outcomes. Therapist factors did not buffer the negative relationship between client negativity and positive therapy outcomes as expected, although there were instances in which therapist factors enhanced a positive relationship between these variables. Actor and partner effects, as well as gender differences, are discussed. The study's implications and limitations are considered as they contribute to understanding how client and therapist common factors influence the course of couple therapy.