Soil nutrient balance is used to evaluate the state of soil fertility, rate of nutrient depletion, sustainability of land productivity, the environmental wellbeing of an area, and to take appropriate management decisions. This study was conducted to quantify soil nutrient balance and stocks on smallholder farms at Agew Mariam watershed in northern Ethiopia in the 2020/21 main season. Inflows and outflows of nitrogen (N), phosphorus (P), and potassium (K) into, and out of barley, tef, and wheat farms were determined through, field measurement, laboratory analysis, USLE model, pedo-transfer functions, and interview questions. The total inflows of N on barley, tef, and wheat farms were 15.1, 12.5, and 10.5 kg ha-1 yr-1 respectively. P inflows on barley, tef and wheat were 0.7, 3.3, and 3.4 kg ha-1 yr-1 respectively. Thus K inflows values were similar for all farms 2.7 kg ha-1 yr-1. The outflow of N was 81.8, 21.4, and 57.6 kg ha-1 yr-1 for barley, tef, and wheat respectively. The outflows of P from barley, tef, and wheat were 6, 1.8, and 5.3 kg ha-1 yr-1 respectively. Similarly, the total K outflows were 15.5, 6, and 8.7 kg ha-1 yr-1 from barley, tef, and wheat farms respectively The N partial balance of barley, tef, and wheat was -66, -9.8, and -50.7 kg ha-1 yr-1 respectively. The P balance was -5.9, 0.9, and -2.6 kg ha-1 yr-1 for barley, tef, and wheat respectively. Whereas, K balance was -12.3, -3.2 and -5.4 kg ha-1 yr-1 from barley, tef, and wheat respectively. The balance results revealed that N and K had negative values except for P in tef. The major paths of nutrient loss were via grain yield, crop residue removal, and leaching. The stock of N was 1295, 1510, and 1240 from barley, tef, and wheat kg ha- 1respectively while, the P stock was 63, 18.7, and 27.5, kg ha-1 from barley, tef, and wheat farms respectively. Similarly K stock was 1092.7, 1059.4, and 1090.6 kg ha-1 from barley, tef, and wheat cropping systems respectively. Reversing the imbalance between inflows and outflows via adding organic and inorganic fertilizers is critically essential.