With concerning the sustainable development in the modern construction industry, this study investigates the effect of adding straw grass (SG) as a new type of natural fiber on the strength and shrinkage behaviors of concrete. Different SG fiber lengths of 3, 5, and 7 cm with a constant amount of 0.4% (by volume) were added to concrete mixtures in order to delve into the mechanical attributes of natural fiber concrete. The experimental analysis demonstrated the advantages of using SG fiber in concrete due to its action as a self-maintaining mechanism and bridging effect that enhanced and strengthened the mechanical strength and drying shrinkage of the concrete significantly. In particular, the addition of longer SG fibers boosted the compressive and splitting tensile strength up to 30% and 131% in comparison with the no SG fiber concrete, respectively. Also, the flexural strength and drying shrinkage of the concrete were enhanced considerably with the addition of SG fiber, especially at the later ages. As a result, the 56-day-old concrete incorporating 7 cm SG fiber obtained a maximum compressive, flexural, and splitting tensile strengths of 51.2, 7.1, and 6.2 MPa, respectively, with a minimum drying shrinkage value of -0.0208%.