Abstract We previously reported that three apple pomace-based Trichoderma inoculants enhanced seedling vigour in pea ( Pisum sativum) germinated in potting soil. The objective of this study was to further investigate the effect of isolated extracts from these bioinoculants on phenolic content and seedling vigour in peas. When pea seeds were pre-treated with Trichoderma viride, Trichoderma harzianum and Trichoderma pseudokoningii inoculant extracts, the germination rate in potting soil increased by, 15, 15 and 20%, respectively, compared with water treatment control. After 5 days of growth, the average plant height increased by 27, 39 and 31%, respectively; the average fresh weight increased by 33, 46 and 36%, respectively. The average phenolic content, another key indicator of vigour identified in our studies, increased by 13, 18 and 17%, respectively. The root elongation during germination of pre-treated pea seeds was more rapid than control. Pea seeds treated for 24 h with the dilution of 10 −2 of Trichoderma inoculant extracts resulted in the most rapid plant growth and highest phenolic content of pea seedlings. The chemical composition of the inoculant extracts was partially characterized.