This study aims to introduce a novel Non-Linear Diophantine Fuzzy Multi-Criterion Decision-Making Model for COVID-19 diagnosis and control. The study is organised into three sections to encourage individuals and to develop an appropriate strategy for emergency decision-making circumstances. First, we propose a generalizations of Pythagorean fuzzy sets, q-rung orthopair fuzzy sets, and linear Diophantine fuzzy set, called Non-linear Diophantine fuzzy set (Non-LDFS) and discussed their important properties. Moreover, mathematical criteria for Non-LDFSs are established based on certain operating laws. In the second part of the study, we propose a set of Non-LDF averaging and geometric aggregation operators for aggregating expert judgments based on TOPSIS techniques. In final part, the newly defined Non-LDF Topsis Method is used to solve a medical diagnosis challenge for the COVID-19 virus, and the findings are reported. To accomplish this, we developed an enhanced ”multi-criteria decision-making” (MCDM) technique that should be capable of evaluating and selecting the best alternative choice of COVID-19 based on five criteria. A comparative analysis is also performed for the novel Non-LDF Topsis, and the prospects of the designed research are addressed.