A bar joist reinforcement apparatus may include a base assembly adapted to be connected to a lower portion of a bar joist, a top assembly adapted to be connected to a top portion of the bar joist, and an adjustable coupling assembly connected between the base assembly and the top assembly for adjusting the distance separating the base and top assemblies. The apparatus may be used to reinforce a bar joist by inserting the apparatus in between upper and lower portions of a bar joist, adjusting the apparatus so the top and base assemblies come into contact with, press against, and/or brace the upper and lower portions of the bar joist, and connecting the apparatus to the bar joist using bolts and conventional tools instead of welding.