SummarySelective autophagy removes harmful intracellular structures such as ubiquitinated, aggregated proteins ensuring cellular homeostasis. This is achieved by the encapsulation of this cargo material within autophagosomes. The cargo receptor p62/SQSTM1 mediates the phase separation of ubiquitinated proteins into condensates, which subsequently become targets for the autophagy machinery. NBR1, another cargo receptor, is a crucial regulator of condensate formation. The mechanisms of the interplay between p62 and NBR1 are not well understood. Employing a fully reconstituted system we show that two domains of NBR1, the PB1 domain which binds to p62 and the UBA domain which binds to ubiquitin, are required to promote p62-ubiquitin condensate formation. In cells, acute depletion of endogenous NBR1 reduces formation of p62 condensates, a phenotype that can be rescued by re-expression of wild-type NBR1, but not PB1 or UBA domain mutants. Our results provide mechanistic insights into the role of NBR1 in selective autophagy.