Previous research suggests that, compared to men, women are more prone to internal attribution of partner's negative behaviour and to a less favourable evaluation of the efficacy of conflict resolving in their marriage. However, the research findings are not completely consistent. The same holds for the findings about the relationship between participants' age and perceived efficacy of marital conflict resolution. Therefore the aim of this study was to examine the sex difference in attributions of partner's negative behaviour (including different dimensions of causal and responsibility attribution) and in self-reported efficacy of marital conflict resolution, as well as the relationship of the marital conflict resolution with attribution dimensions and participants' age. Data were collected through online survey comprising a set of questions about participant’s socio-demographic characteristics, Relationship Attribution Measure and Marital Conflicts Resolution Efficacy Scale. Participants in the study were 456 individuals, specifically 416 females and 40 males. Sex differences in attribution of partner's negative behavior and in the perceived efficacy in resolving marital conflicts were not tested because of the very small number of male participants, especially compared to female participants. The correlation between participants’ age and reported efficacy in marital conflicts resolution was not significant. Perceived efficacy in marital conflict resolution was negatively associated with causal and responsibility attributions of the partner’s negative behavior; that is, participants who reported being more effective in resolving the conflicts were less likely to attribute such a behavior to internal, stable, and global causes, as well as to perceive the partner as being responsible and blameworthy.