Speed of development, speed to market, and meeting market needs are often recommended in the new product development (NPD) literature as keys to successful product launches, but it is not clear how market knowledge competence and time performance are related in driving successful NPD. To find out, we analyzed 250 firms from four countries (Germany, Italy, Japan, and USA). We found the two factors to be complementary, i.e., both direct and interaction effects of speed and market knowledge on product success were found. In particular, the strong effect of market knowledge competence on product success is noteworthy because building market knowledge competence is a strategy that management can proactively utilize to cope with market uncertainty, which has been argued to moderate the time performance relationship in NPD. The implication is that both measures of effectiveness (matching needs) and efficiency (speed) need to be considered complementarily when managing for successful NPD.