Several methods for early pregnancy diagnosis in ruminants have been developed. Some of them are applicable in the field, but not enough accurate. Hence, the aim of this study was to investigate pregnancy detection in goats at earlier stages, that is, 7, 14, 21, and 28 days post-artificial insemination (post-AI). Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE gel electrophoresis) was used to determine the pattern of protein expression. Moreover, ultrasound was used to confirm pregnancy 45 days post-AI. Nine of female goats were under ovsynch protocol and mating was initiated. The results showed that the pattern of protein expression was different between pregnant and non-pregnant goats with molecular weights of 42 kDa and 52 kDa. The protein fraction at 42 kDa was higher on day 21 and 28 post AI. In addition, the 52 kDa protein fractions was higher at day 7, 14, 21, and 28 post-AI in pregnant than in the non-pregnant goats. Ultrasonography was used 45 days after AI to confirm the results of SDS-PAGE gel electrophoresis. The ultrasound results were consistent with SDS-PAGE gel electrophoresis. Therefore, serum protein fractions of 42 kDa and 52 kDa might serve as protein biomarkers for early detection of pregnancy in goats.