The purpose of the experiment was to determine how the addition of dehydrated alfalfa (DA) and ascorbic acid (AA) into the diet of hens influences the performance characteristics and egg quality characterised by physical parameters, yolk carotenoid content, and the oxidative stability of yolks. Two hundred and forty Hisex Brown hens were divided into 6 treatment groups according to the level of DA (0 and 40 g/kg) and concentration of AA (0, 100, and 200 mg/kg) in the diet. Hen-day egg production and egg mass production were reduced by the supplement of DA (P < 0.001) and AA (P = 0.017). The addition of DA itself increased the feed intake per egg (P < 0.001) and the feed conversion ratio (P < 0.001). The heaviest eggs (P < 0.001) were laid by hens fed a diet with 100 mg/kg of AA (67.6 g). The AA supplement improved egg content quality, i.e., Haugh units (P < 0.001), albumen index (P < 0.001), and yolk index (P < 0.001), whereas the addition of DA increased values of yolk colour (P < 0.001) and had a negative effect on shell quality. The interaction of DA and AA was detected in the zeaxanthin concentration in the yolks (P = 0.002). The highest concentration was found in eggs from hens fed a diet with a DA supplement and 100 or 200 mg/kg of AA (17.33 or 17.25 mg/kg dry matter of yolk). In addition, 40 g/kg of DA significantly increased the concentration of other carotenoids, lutein (P < 0.001) and β-carotene (P < 0.001) in the yolks and increased the oxidative stability of fresh eggs (P < 0.001). The results suggest that adding DA in the amount of 40 g/kg to the hen diet provides a good source of carotenoids and, in combination with AA, a better deposition of carotenoids in egg yolks. On the other hand, DA deteriorates performance and shell quality.