Two experiments were conducted on head lettuce (Lactuca sativa) simultaneously grown in Bosaily (on the north coast of the Nile Delta) and Dokki, Giza, for the two successive seasons of 2020/2021 and 2021/2022. This work investigates the practical simple applications that overcome low lettuce head quality and yield under different climatic conditions. Three treatments were applied, i.e. foliar spray with salicylic acid (500 ppm), chitosan (150 ppm), and the control (tab water) five times, 10 days apart, starting from mid-December (about 3 weeks after transplanting). Each treatment was replicated three times in completely randomized plots. Lettuce heads were harvested after 105 days for chemical analyses and vegetative growth trial assessment. The chemical analysis included total sugar (g/100g D.W); nitrate (mg/kg D.W); total phosphorus and total potassium (mg/100 mg D.W). Plant growth and yield data included the total number of leaves, head diameter, head firmness, and fresh and dry weights from three heads per replicate. Total yield and total marketable yield were estimated in tons per feddan. The results indicated that head lettuce gave significantly higher vegetative growth, and higher total and marketable yield in chitosan treatment followed by salicylic acid, compared to the control. The total yield from El-Bosaily location was 23.6, 25.2, and 24.3% than Dokki for control, salicylic acid, and chitosan, respectively. Salicylic acid and chitosan gave 42.8 and 68.6% higher than control in El-Bosaily, and 41.0 & 67.7% in Dokki, respectively. Bosaily site gave significantly higher yield than Dokki.