The aim of the study was to determine the risk factors of unusual, lateral direction of epiphyseal displacement in primarily unilateral slipped capital femoral epiphysis (SCFE) patients with a special focus on radiological parameters of an unaffected hip. A total of 115 patients (75 boys, 40 girls), mean age 13.2 years (8.4–18.6), were analyzed. The mean follow-up time was 11 years (2–29). The proportion of valgus slip among SCFE patients was 11 of 115 cases (9.6%). The patients with valgus slip compared with the classic ones were predominantly females (55 vs. 33%), were younger (11.1 vs. 13.4 years), had a greater epiphyseal-shaft angle (67.4 vs. 59.1°), smaller displacement in the frontal plane (absolute value 6.7 vs. 15°), and a lower risk of contralateral slip (27 vs. 65%). There was no difference in the neck-shaft angle and epiphyseal-neck angle value. A more horizontal orientation of the subcapital growth plate, assessed by epiphyseal-shaft angle, can be considered a conducive factor in the valgus direction of epiphyseal slip in SCFE. In valgus SCFE cases, there is a smaller degree of epiphyseal displacement in both the sagittal and the coronal plane and a lower risk of consecutive contralateral slip.