Background We aimed to compare employment conditions, psychosocial working conditions, and prevalence of low back pain among migrant and local construction workers in Argentina. Methods In a cross‐sectional study among workers from three contracting and eight subcontracting companies as well as 26 construction sites in the region of Buenos Aires, Argentina, 134 out of 150 local (89% response) and 141 out of 150 migrant construction workers (94% response) answered a validated questionnaire. Psychosocial working conditions were evaluated based on an imbalance between efforts and rewards (ERI). Results Compared to local workers, migrants were younger, more likely to work without a contract (57% vs 8%), to report ERI (81% vs 18%) and to suffer from low back pain during the 7‐days before study (80% vs 42%) (all P < .0001). After mutual adjustment, being a migrant (prevalence ratio 2.1; 95% confidence interval [CI] 1.4‐3.0) and working without a contract (1.7; 95% CI, 1.4‐2.1) were statistically significant risk factors for low back pain. Conclusions This study describes the precarious situation of migrant workers in the Argentinian construction industry and the potential health consequences. Provision of formal employment relations might help to better protect migrant workers’ safety and health. Prospective studies are needed to assess the causes and effects of the findings we describe.