Single crystals of erbium tri-fluoromethanesulfonate (ErTFMS) were prepared from the slow evaporation of the aqueous solution. The principal magnetic susceptibilities perpendicular to the c-axis of the hexagonal crystal was measured down to 13K. Principal magnetic anisotropy was also measured from 300K down to 80K which provides principal susceptibility parallel to the c-axis down to 80K. A very good theoretical simulation of the thermal variation of principal magnetic susceptibilities of ErTFMS has been obtained with a crystal field (CF) of C 3h site symmetry, in which J-mixed eigenvectors and intermediate coupling effects have been used. No ordering effects were noticed down to the lowest temperature (13K) attained, indicating the inter-ionic interaction to be of predominantly dipolar type. The g-values are found to be g ∣∣ =8.86 and g ⊥ =1.62, respectively. The Schottky anomaly in the electronic heat capacity at about 80K has been computed from the Stark pattern. The thermal behavior of quadrupole splitting and hyperfine heat capacity were calculated from the CF analysis.