This thesis considers whether acquiring host-country citizenship affects the labour market integration of immigrants. I conduct an empirical analysis of whether naturalisation affects occupational status using a panel of employed immigrants in Norway from 2003-2013. I first examine whether Norwegian citizenship improves access to jobs in the central government and the broader public sector, consistent with the removal of formal employment barriers. I then assess whether acquiring Norwegian citizenship shifts immigrants into white-collar and high-skilled jobs, insofar as naturalisation promotes human capital accumulation or acts as a positive signal to employers. After accounting for endogenous selection into citizenship by controlling for individual fixed effects, I find that naturalisation is associated with lower employment probabilities in the central government and public sector, and no statistically significant effect on employment in white-collar and high-skilled jobs. Effects vary by gender and region of origin. In particular, the negative naturalisation effect in the central government appears to be primarily driven by women from Africa, Asia, and Latin America, while the same effect in the public sector is primarily driven by Eastern European men. There is also evidence that adopting Norwegian citizenship shifts women from Africa, Asia, and Latin America into white-collar jobs, while concurrently shifting some groups into and others away from high-skilled jobs, though these results are sensitive to the particular specification used. Potential sample selection issues and data constraints are also addressed. These results are consistent with previous studies in Norway, but in stark contrast to findings in other immigrant-receiving countries. The absence of a positive naturalisation effect in Norway is discussed in light of country-specific labour market features and possible behavioural responses among the naturalised.