Marker-free transgenic Camelina sativa (L.) plants carrying a synthetic gene for cecropin P1, an antimicrobial peptide, under the control of the cauliflower mosaic virus 35S RNA promoter have been obtained and analyzed. The plants were transformed with an agrobacterial binary vector free of selection genes of antibiotic and herbicide resistance. The marker-free transformants were screened via measurement of the antibacterial activity of cecropin P1 and enzyme immunoassay. The obtained plants exhibited an increased resistance to infection with the bacteria Erwinia carotovora, the fungi Fusarium graminearum, and oxidative stress during infection. Analysis of the fatty acid composition of seed oil showed an increased amount of α-linolenic acid in the transgenic Camelina lines as compared to unmodified plants. The results indicate that the cecropin P1 gene can be included in an integral, antistress, plant-protective system.