Application of soil conditioners is a soil conservation method to increase aggregate stability by reducing clay dispersion and increasing inter-particles’ bonding. Therefore, soil physical condition and plant growth will be improved by the use of soil conditioners. Earthworms are also useful for soil health, diminishing land degradation and protection of environment. They have an important role in enhancing soil physical quality, organic matter dynamics and nutrients cycling. This study was conducted to investigate the effect of six conditioners including polyacrylamide (PAM), orthophosphate (OP), phytic acid (PA), humic acid (HA), earthworm’s mucus (M) and azolla protein extract (AZ) with three concentrations (0, 10 and 20 mg/l) on soil structural stability and quality indicators such as water repellency, soil organic carbon (SOC), percent of water-stable aggregates (WSA), water-dispersible clay (WDC), high energy moisture characteristic (HEMC) indices, soil water characteristic curve (SWCC), tensile strength (ITS) and friability indices ( F 1 and F 2 ) in two loam and sandy loam soils. Then, several indicators and quantities including field capacity ( ? FC ), permanent wilting point ( ? PWP ), available water (AW 330 ), macroporosity (Macro-P), mesoporosity (Meso-P), microporosity (Micro-P), air capacity (AC) and Dexter’s soil physical quality index ( S Dexter ) were calculated and evaluated. The analysis of variance and means’ comparisons were done based on three-factor factorial arrangement of treatments in a completely randomized design. The results showed that application of some conditioners increased soil structural stability (i.e., lower WDC and higher WSA). In both soils, using M and AZ significantly reduced WSA. In the loam soil with greater clay content, the effect of conditioners in diminishing structural instability was greater than that in the sandy loam soil. The influence of conditioners on soil water repellency was insignificant. Adding PAM to loam soil increased water retention in the high-energy range (i.e., HEMC) compared to the control. However, adding other conditioners to sandy loam soil decreased water retention compared to control. Application of M and AZ decreased soil friability as quantified by F 1 and F 2 ; this finding might be related to high sodium concentration in mucus and high decomposability of azolla’s extract. An increment in concentration of HA (from 10 to 20 mg/l) increased ITS, but the same increment for AZ decreased ITS. In the loam soil, SWCCs for both concentrations of OP, PAM, HA and PA located upper compared to control and indicated greater water retention in the wet range. In the sandy loam soil, SWCCs for both concentrations of PAM, HA and PA located upper compared to control. Therefore, application of conditioners increased water retention in the wet range more than that in the dry range, and as a consequence soil structure and physical quality were improved. In general, AZ and M reduced Macro-P and Meso-P and degraded soil structure. Humic acid was the best in terms of Meso-P. Overall, AZ and M increased relative field capacity and S Dexter in the loam soil, and AC, AW 330 and saturated water content in the sandy loam soil. With an increment in the concentration of conditioners (from 10 to 20 mg/l), AC became greater in loam than in sandy loam, ? FC was greater in sandy loam than in loam, and ? PWP increased in both soils. Keywords : Soil conditioners, Soil water repellency, Dispersible clay, High energy moisture characteristic, Soil structural stability, Soil tensile strength, Soil friability