Phosphorus (P) deficiency is a critical environmental constraint that affects the growth and development of several legume crops that are usually cultivated in semi-arid regions and marginal areas. P-deficiency is known to be a significant limitation for symbiotic nitrogen fixation (SNF), and variability in SNF is strongly interlinked with the concentrations of inorganic phosphate (Pi) in the nodules. To cope with P-deficiency, legumes trigger various adaptive responses, including the induction and secretion of acid phosphatases (APases) and phytases, maintenance of Pi homeostasis in nodules and other organs, and improvement of oxygen consumption per unit of nodule mass. While the induction of phytases is a universal response to P-deficiency in higher plants, the physiological role of these enzymes in nodules of N2-fixing legume is crucial but still not fully understood. Understanding the role of APases and phytases activities in response to environmental constraints may be important in developing strategies to improve the tolerance of the nodulated legume to low-P availability. In this review, we summarize and discuss recent advances in the understanding of the expression of phytases within the nodules of legumes under P-deficiency and address whether this expression might influence the nodule respiration and contribute to adaptation of N2 fixing legumes to low-P environments. Finally, we will provide perspectives on future directions for research in this field.