Eradication of toxic heavy metals from waters polluted due to urbanization and industrial effluents is a burning issue. There is a need to enhance research to find out new economical methods to overcome problems associated with current removal techniques. Use of novel modified biosorbents to increase metal removal efficiency through biosorption is the most suitable alternative. The present study is focused on removing cadmium and tin metal ions using acid-pretreated wheat straw (PWS) and urea-modified wheat straw (UMWS). The biosorption process is carried out in batch fashion to optimize the basic conditions of the process such as pH, amount of biosorbent, time of contact, agitation speed, and temperature. Langmuir isotherm, Freundlich isotherm, and Dubinin-Rudikish (D-R) model were applied to determine the maximum amount of metal ions adsorbed and the feasibility of the process. The maximum amount of cadmium and tin metal ions adsorbed using PWS is 33.55 (mg/g) and 47.84 (mg/g), whereas using UMWS is 74.62 (mg/g) and 64.10 (mg/g), respectively, as calculated by Langmuir model. Kinetic studies showed a better fit for pseudo 2^nd-order, whereas intra-particle diffusion and Bangham’s models partially proved macro pore diffusion as a rate-determining step. Thermodynamic studies confirmed that the process was spontaneous and endothermic with negative values of Gibb’s free energy and positive values of enthalpy and entropy changes. It was found that modification enhanced the metal binding capacity up to more than 100%. As urea and wheat straw both are biodegradable, the process became eco-friendly.