This paper presents the first decadal quantification of glacier area in the cordilleras Carabaya and Apolobamba in Peru and Bolivia (14 degrees 00'-14 degrees 39'S; 69 degrees 14'-70 degrees 19' W). We calculated the changes in glacier area between 1975 and 2015 and the number of glacial lakes between 1985 and 2015 using Landsat images. Glacier shrinkage in our study region was most likely to have caused the expansion of numerous glacial lakes in recent decades. In contrast to observed glacier fluctuations in the western cordilleras of the tropical Andes, continuous glacier shrinkage was observed in the eastern cordilleras of Peru and Bolivia. The estimated glacier mean area loss between 1975 and 2015 in the Cordillera Apolobamba and the Cordillera Carabaya was about 51% and 79%, respectively. Glaciers situated below 5000 m a.s.l. nearly disappeared (93% and 95.5% in the cordilleras Apolobamba and Carabaya, respectively) during this period, but glaciers above 5500 m a.s.l. were relatively stable (13.5% and 31% in Apolobamba and Carabaya, respectively). Further on, glacier area loss by aspect revealed that glaciers oriented towards the Amazon Basin were retreating faster (74.5% and 86%, respectively) than those oriented towards the Pacific coast (40% and 68%, respectively). We observed the formation of 206 new glacial lakes between 1985 and 2015 in these two mountain ranges with an increase in the total area of 3.8 km(2), which is a significant growth in just 30 yr.