For legislators without legislative experience, credibility can be vital to achieving legislative success, and expertise from one’s professional background is a highly plausible source of such credibility. For example, when legislating in policy areas directly related to one’s previous occupation, a legislator’s colleagues may perceive policy instruments as more informed by expertise rather than ideological preferences. In this paper, I focus on several questions related to the linkage between professional background and legislative success, and specifically, the ability to guide authored bills through the legislative process. First, does a match between a legislator’s professional background and the topic of legislation make that legislation more likely to advance in the legislative process? Second, if so, does the importance of professional background dissipate as length of legislative service increases? Third, does the relevance of professional background systematically differ across types of legislators and legislatures? I find strong evidence that having a relevant professional background does lead to legislative success for new members, but that this pattern persists later in the legislative career too. Moreover, I find that these patterns are especially strong for minority party legislators and in legislatures with higher levels of membership turnover.