We report direct measurements of interactions, dimensions, and solution behavior of adsorbed nonionic and zwitterionic triblock copolymers as a function of aqueous [NaCl] and [MgSO4] in the range 0-1 M. Total internal reflection microscopy is used to measure kT- and nanometer-scale interactions between hydrophobic colloids and surfaces with adsorbed triblock copolymers with central poly(propylene oxide) (PPO) blocks and end blocks of the following: poly(ethylene oxide) (PEO), poly(3-(N-2-methacryloyloxyethylN,N-dimethyl) ammonatopropanesulfonate) (PMAPS), and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC). The findings indicate the following qualitatively different and unique behavior for each polymer: PEO layers are [NaCl]-independent but collapse and become less repulsive and eventually attractive with increasing [MgSO4]; PMAPS layers are increasingly repulsive and extended with increasing [NaCl] but become less repulsive/extended with increasing [MgSO4]; and PMPC layers are completely insensitive to both [NaCl] and [MgSO4]. A competition between solvated molecular interactions and structures appears to explain the unique response of each polymer to nonspecific and specific ion effects as a function of aqueous salt solution composition.