This article investigates the algebraic non-routine problem-solving skills of grade 12 learners of a high-achieving school in northern Namibia. The school was selected on the basis of its outstanding results and sound management style. The study followed a descriptive survey design that involved a written test to examine learners' problem-solving skills together with the solution strategies used, and structured learner interviews to get their views about the choice of strategies for solving non-routine problems. The assessment framework of the learners' problem-solving skills was based on the Trends in International Mathematics and Science Study (TIMSS) scales for Polya's problem-solving model. The results showed that learners were more successful in answering the question with a diagrammatic illustration, suggesting that the use of diagrams makes it easier to understand the problems. A significant number of learners' algebraic problem-solving skills function at or below level 2 of TIMSS scale. The algebraic strategy was the most preferred solution strategy and there were learners who encountered difficulties with the language used in the questions.