In order to investigate maternal recognition in the koala, this study used a combination of endocrinology and proteomics to identify potential pregnancy biomarkers. Plasma progesterone levels and the proteome of the koala luteal phase were investigated in pregnant (n = 4), mated but non-pregnant (n = 4), and GnRH ovulation induced (non-mated) females (n = 7). Plasma samples were collected on the day of mating or GnRH injection (D0) and multiple days (D) post mating/GnRH injection for the duration of the luteal phase. Progesterone was measured by enzyme-linked immunosorbent assay. While AUC analysis revealed no significant difference in overall progesterone concentration profiles across the treatment groups over the course of the luteal phase, the mean progesterone concentration of pregnant females on D2 was significantly higher than GnRH treated females (40.7 ± 3.33 ng/ml vs 15.71 ± 1.83 ng/ml). Plasma also underwent FASP digestion and analysis by LC-MS/MS with SWATH acquisition. Overall, 158 proteins were identified across the treatment groups. At D2, circulating LRG1 (an acute phase-like protein) was significantly more abundant in mated females compared to GnRH treated females. LRG1 was also elevated at D2 in the plasma of pregnant koalas and then significantly declined on D9 and D19. At the expected time of maternal recognition (D9), 5 additional proteins were detected in pregnant females when compared to those that ovulated but failed to produce pouch young and those only treated with GnRH; one such protein was an albumin isoform. As progesterone rose (D20), an inter-a-trypsin heavy chain 4 (ITIH4) like molecule was only detected in pregnant females. Biomarkers of interest will be further profiled by ELISA to determine their value for early pregnancy detection and embryonic loss. The outcomes of this projects will aid in understanding maternal recognition in koalas and assist management of captive koala breeding programs.