The study was carried out during 2019-2020 and 2020-2021 seasons at Badaway, Al-Dakahlia Governorate, Egypt, using 20-year-old trees in commercial orange and guava orchards in which standard horticultural practices of commercial production were being carried out. The orange cultivar grown was “Washington navel orange" (C. sinensis) budded on sour orange (C. aurantium) rootstocks, with tree planting spaced at 5 x 5 m. For the guava (P. guajava) experiment, the cultivar “cv. Maamoura" This study was conducted during two seasons in 2019 and 2021 in Badaway, Al-Dakahlia Governorate, Egypt, to investigate the influence of some pre and post-harvest treatments on yield parameters, quality and self life of Washington Navel Orange and guava “cv. Maamoura." The experiment was laid out in Factorial Randomized Block Design with three replications. Among four different pre-harvest treatments, the treatment which comprised of 1.5% calcium chloride has recorded the highest fruit weight (332.93 and 168.19 g), yield (100.77 and 81.65 kg/tree), fruit firmness (25.10 and 11.77 kg/cm²),TSS percentages (16.10 and 14.13 %), titratable acidity% (1.19 and 0.63 %), ascorbic acid content (Vitamin C) (61.99 and 197.51 mg/100 ml juice) and total sugars percentage (11.55 and 10.55 %) of Washington navel orange and guava when compared to the control, respectively. The best performed trees which have received the treatment of calcium chloride at 1.5% were taken for postharvest treatment study with six treatments [Distilled water (control), Citric acid at 1%, Rosemary oil 4 %, Coconut oil 4 %, Moringa oil at 4 % and Peppermint oil 4 %]. It was found that the combined effect of the pre-harvest treatment with 1.5% calcium chloride with post harvest treatment of Moringa oil at 4% has increased the firmness (20.11 and 9.66 kg/cm²), ascorbic acid content (68.31 and 200.55 mg /100 ml juice) and shelf life (35.33 and 10.20 days) and decreased physiological loss in weight (3.23 and 8.22 %), TSS (16.70 and 10.22 %), acidity (0.98 and 0.58 %), reducing sugar (4.07 and 5.17 %) and peroxidase activity (38 and 115 mg protein/min) of Washington navel orange and guava fruits stored under room temperature, respectively.