Interactions occurring in foods at acidic pH are important for improving the colloidal stability of protein suspensions. This study evaluated the binding between pea albumins (PA) and anionic soluble pea polysaccharides, comparing them to β-lactoglobulin (β-lg) and high methoxyl pectin (HMP). High-/low methoxyl soluble pea polysaccharides (HM-/LM-PPS) and HMP were first analyzed by size exclusion chromatography coupled with multi-angle light scattering to determine molar mass distribution. Then, the interactions with albumins were quantified using isothermal titration calorimetry (ITC) at pH 4. In all cases, complex formation was exothermic with Gibbs free energy between -6.5 to -8.8 kcal/mol. Enthalpy was found to be the main driving force for complexation of HMP and LM-PPS, while both entropy and enthalpy contributions were important for the HM-PPS-protein complexation. β-lg showed a higher binding affinity compared to PA to the polysaccharides. This research highlights the potential of pea soluble polysaccharides as a functional food ingredient.