There is a tendency of warming and wetting in northwestern China in recent decades. However, less is known about whether or not tree growth shows an increasing trend. In this study, we developed three tree-ring width chronologies of Picea schrenkiana in the northern Tianshan Mountains to assess changes in the radial growth of P. schrenkiana and to discuss the stability of the relationships between tree growth and climate. Three chronologies all showed that the tree-ring index has declined significantly since the 1960s. At two western sites, the growth of P. schrenkiana was negatively affected by the summer temperature of the previous year. At the eastern site, early summer temperature-induced drought of the current year was the key factor affecting tree growth. The result of moving-window correlations was consistent with correlation analyses. Spatial correlation analyses revealed that variations in tree-ring width could respond to a wide range of temperature changes in northwestern China, especially in the past half century. We expect that climate warming hinders the radial growth of P. schrenkiana in the northern Tianshan Mountains. Our study also helps to clarify the characteristics of tree growth in northwestern China under the influence of westerlies.