This experiment was conducted to investigate the effects of different net energy (NE) concentrations of diets on the growth performance of growing or finishing pigs housed individually. In experiment 1 (growing pigs), a total of 60 growing pigs (Landrace × Yorkshire × Duroc; initial BW = 34.3 ± 3.7 kg) were allotted to 5 dietary treatments with 12 replicate pens and 1 pig per pen in a 35-d feeding trial. In experiment 2 (finishing pigs), a total of 60 finishing pigs (Landrace × Yorkshire × Duroc; initial BW = 73.7 ± 5.6 kg) were allotted to 5 dietary treatments with 12 replicate pens and 1 pig per pen in a 28-d feeding trial. Within each experiment, a corn-soybean meal-based basal diet (91.75%) was prepared to meet all nutrient requirements for growing or finishing pigs (NRC, 2012). The remaining portion (8.25%) was added to the basal diet by different inclusion ratio of soybean oil and starch to create 5 NE concentrations (2,318, 2,390, 2,462, 2,533, or 2,605 kcal NE/kg) of diets for growing or finishing pigs. The NE and amino acids concentrations in diets were calculated based on the values from NRC (2012). Pigs were allowed ad libitum access to feed and water in both experiments. Statistical model included dietary treatment as a fixed effect. Orthogonal polynomial contrast test was performed to determine linear and quadratic effects of NE concentrations of diets. Results indicated that the final BW, ADG, ADFI, and feed efficiency (G:F) of growing pigs were not affected by dietary treatments. Similarly, final BW, ADG, and ADFI of finishing pigs were not affected by dietary treatments. However, the G:F of finishing pigs was improved (linear, P < 0.01) with increasing NE concentrations in diets (0.326, 0.331, 0.323, 0.352, and 0.349 for 2,318, 2,390, 2,462, 2,533, or 2,605 kcal NE/kg, respectively). In conclusion, increasing NE concentrations in diets from 2,318 to 2,605 kcal/kg have no beneficial effects on the growth performance of growing pigs, but improve feed efficiency of finishing pigs.