Objectives: Immunoparesis (IP) is a risk factor associated with an unfavourable outcome in several plasma cell disorders. It has been suggested that its presence in light-chain (AL) amyloidosis could be associated with worse prognosis. However, the relevance of IP after treatment has not been evaluated to date. The aim of this study was to determine the prognostic impact of IP at diagnosis and one year after treatment onset in patients with AL amyloidosis. Methods: The clinical records of 69 patients with AL amyloidosis treated at a single institution from January 2006 to January 2016 were included in the study. Results: IP was observed in 27.5% of patients at diagnosis. The presence of IP was associated with a lower probability to achieve very good partial response or better after first-line treatment (37.8% versus 62.2%; p = .04). However, only in the group of patients treated with autologous stem cell transplantation (ASCT), the presence of IP resulted in a shorter progression-free survival (PFS) (30.2 months versus not reached NR; p = .02) but not in overall survival (OS). Persistence of IP at one year after treatment onset was identified in only four (9.8%) of the 41 evaluable patients. In the ASCT group, the absence of IP at one year after treatment onset resulted in a longer median PFS and OS (NR versus 22.6 months; p = .006; and NR versus 35.2 months; p < .001; respectively). In the multivariate analysis, the absence of IP at one year after treatment onset was independently associated with longer survival. Conclusion: IP at diagnosis has a negative impact on survival while its absence at one year after treatment is an independent marker for long-term survival.