Dwarf pine (Pinus mugo Turra) thickets are a substantial land cover in high-elevation mountain ecosystems in Europe, where they fulfill important functions in soil conservation and as wildlife habitat. In many areas across Europe these thickets have rapidly expanded over the past decades because of changing climate and land use, highlighting the need to better understand how species spread relates to growth traits and changing environmental conditions. We quantified changes in dwarf pine cover by elevation on 2 mountains in the Western Carpathians (Central Europe) over 64 years (Babia hora) and 40 years (Pilsko), and we linked them to species growth responses to climate using archival photogrammetry and stem length measurements. We correlated mean growth chronologies with mean monthly temperature and precipitation to assess the main climatic factors driving growth. The total expansion of dwarf pine cover was substantial (28.6% in Babia hora and 57.1% in Pilsko), but the rate of expansion varied with elevation, site, and intra- and interspecific competition. The largest expansion occurred in the open stands of the high elevations (1550–1650 m). Statistically significant positive correlations between growth and temperature were recorded for the most recent growing season and for the preceding growing season. However, despite rising temperatures over time, mean species growth during the last 20 years decreased slightly. The correlation of growth with precipitation was mostly positive but not statistically significant. Thus, the impact of changing climate appeared too weak to overcome other influential factors (eg decline in grazing and intra- and interspecific competition).