Thermally-induced microstructure and property alteration of nano-multilayer (NML) coatings are of principal importance for industrial applications. The phenomenon of surface outflow of confined metal is highly promising for the development of NML-based brazing fillers for joining technology. Annealing conditions, such as temperature and atmosphere, are the principal factors defining the brazing filler outflow characteristics besides the NML design. The present study addresses the microstructure evolution of Ag/AlN NMLs during thermal treatment in various atmospheres (Ar, air, vacuum). The mechanisms of the NML bulk microstructure modification do not change with the annealing atmosphere. Channels in the NML volume are formed at each annealing atmosphere by grain boundary grooving, which act as pathways for Ag atoms transport to the NML surface, causing metal outflow. However, a significant effect of the atmosphere on the metal outflow and shape of the particles formed was observed. Annealing in an inert atmosphere and vacuum results in a moderate surface outflow of Ag atoms. On the contrary, heat treatment in air results in a chemical interaction of nanolayers with oxygen, substantially intensifying the outflow. This interaction is rationalized by considering the surface energies of Ag/AlN and Ag/Al2O3 interfaces, where the latter are formed upon annealing. Based on grooving angles, the upper bound Ag(111)/AlN(0001) interface energy estimate of 0.54 J/m2 at 650 °C was derived, which is significantly lower than the average magnitude of Ag/Al2O3 interface energy (~ 2 J/m2 for crystalline phases). Besides, the annealing atmosphere has an impact on the shape (elongated whiskers, bulk faceted crystals) of Ag particles formed on the NML surface by modifying silver surface energies. The proper choice of a heat treatment atmosphere provides an innovative pathway for controlling the Ag surface outflow in Ag/AlN NMLs for novel low-temperature joining applications. Display omitted •Annealing in air results in a larger Ag outflow than annealing in Ar or vacuum•At each annealing atmosphere, channels in the nano-multilayer volume are formed•The annealing atmosphere affects the shape of Ag particles formed on the surface•Chemical driving forces and stress relaxation are at the basis of Ag outflow•The estimate of Ag(111)/AlN(0001) interface energy at 650 °C is 0.54 J/m2