Objective: Studies in the USA suggest that the association between maternal birthplace, socioeconomic status (SES), and low birth weight (LBW) can vary across different immigrant groups. Less is known outside the USA about these associations. Our study assesses the association of maternal birthplace and SES on the likelihood of LBW infants in Quebec, Canada. Methods: Using 2000 Quebec birth registry data, logistic regression was used to examine differentials in LBW according to maternal birthplace and SES. Singleton infants born to Quebec mothers (n=47,988) were grouped into nine regions based on maternal birthplace: (1) Canada; (2) the USA and western Europe; (3) eastern Europe; (4) Latin America; (5) the Caribbean; (6) Sub-Saharan Africa; (7) north Africa and Middle East; (8) South Asia; and (9) East Asia and Pacific. SES was classified into four categories according to maternal educational attainment: (1) low SES (<11 years); (2) medium-low SES (11-12 years); (3) medium-high SES (13-14 years); and (4) high SES (more than 14 years). Covariates included maternal age, gestational duration, and parity. LBW was defined as between 500 and 2499 g. Results: Compared to a LBW prevalence of 4.5 for Canadian-born mothers, South Asian- and Caribbean-born mothers had prevalence percentages of 9.2 and 8.2, respectively. After adjusting for SES and other covariates, the likelihood (odds ratio (OR), 95% confidence intervals (CI)) of LBW outcomes remained greater for South Asian- (OR 2.84; 95% CI, 1.90-4.24) and Caribbean-born mothers (OR 1.52; 95% CI 1.11-2.10). After pooling these two groups and testing for moderation by SES, we found that high SES immigrant mothers (OR 3.82; 95% CI 2.33-6.25) had a higher likelihood of LBW infants than low SES mothers (OR 2.00; 95% CI 1.22-3.33) compared to high SES Canadian-born mothers. Discussion: In Quebec, the association between foreign-born status and LBW varies according to maternal birthplace.