Vitamin D is a pleiotropic hormone, widely controversial for its role in the development of chronic diseases and cancers, including haematological malignancies, and also for its impact on overall survival. Observational and interventional studies are being conducted on hypovitaminosis D and haematological malignancies and their subtypes in order to improve the therapeutic management of patients. We carried out a prospective observational study over three years on a population of 251 patients followed up for newly diagnosed haematological malignancies to investigate the impact of vitamin D deficiency on this category of patients. Our population was dominated by the lymphoproliferative syndrome and included 125 patients (49.8%). Anthropometric data showed a significant difference in body mass index between the sexes with a p value of 0.001. Vitamin D levels at diagnosis were inadequate in more than half the patients (56%). This hypovitaminosis was linked to the female sex (p = 0.006), obesity (p = 0.031) and the digestive involvement of the lymphoma (p = 0.03). There was also a relationship between vitamin D deficiency and hypoalbuminemia (p = 0.02). This relationship was confirmed in multivariate analysis, with hypoalbuminemia being a factor associated with the deficiency (p = 0.022, OR = 0.95, IC95% 0.91-0.93). However, we did not find any impact on overall survival.