In this work, the partial isothermal section of the Al-Ca-Zn system in the region between 33.3 and 100 at.% Ca has been investigated at 350°C using key alloys. The actual composition of the alloys is measured by inductively coupled plasma technique. Phase relations and solubility limits of the binary and ternary compounds have been determined by means of electron probe microanalysis and X-ray diffraction. In the current work, a new ternary compound has been identified in this region with the Al9Ca31Zn10 (IM1) composition. Binary compound Al14Ca13 (IM2) has an extended solid solubility into the ternary system. The homogeneity ranges of the Al2Ca, the MgNi2-type C36 phase Al2-xCaZnx (0.28≤x≤0.70) (IM3) at 350°C and CaZn2 compounds in the pseudobinary Al2Ca-CaZn2 section have been determined at 350°C and the results are combined with the literature to construct the partial vertical Al2Ca-CaZn2 section and partial isothermal Al-Ca-Zn section at 350°C.