A boron nitride powder includes boron nitride aggregated grains that are formed by aggregation of scaly hexagonal boron nitride primary particles, the boron nitride powder having the following characteristic properties (A) to (C): (A) the primary particles of the scaly hexagonal boron nitride have an average long side length of 1.5 μm or more and 3.5 μm or less and a standard deviation of 1.2 μm or less; (B) the boron nitride aggregated grains have a grain strength of 8.0 MPa or more at a cumulative breakdown rate of 63.2% and a grain strength of 4.5 MPa or more at a cumulative breakdown rate of 20.0%; and (C) the boron nitride powder has an average particle diameter of 20 μm or more and 100 μm or less. Also provided are a method for producing the same and a thermally conductive resin composition including the same.