The study sought to find out difficulties encountered by high school chemistry students when solving stoichiometric problems and how these could be overcome by using a problem-solving approach. The study adopted a quasi-experimental design. 485 participants drawn from 8 highs schools in a local education district in Zimbabwe participated in the study. A validated stoichiometry achievement test was used to collect data at pre-test and post-test stages. The researchers also prepared a difficulty identification index to analyse the difficulties encountered by students. Quantitative data was analysed using inferential statistics and ANCOVA. From the findings, the difficulties identified were lack of understanding of the mole concept, inability to balance chemical equations, use of inconsistent stoichiometric relationships, identifying the limiting reagent, determination of theoretical yields and identification of substances in excess. The study also found that the use of problem-solving instruction as effective in remedying the identified difficulties in comparison to the conventional lecture method. It was strongly recommended that chemistry educators should analyse and understand student difficulties if they are to assist the learners to become confident and efficient problem solvers. Furthermore chemistry educators should implement the problem-solving pedagogical technique as a means of addressing the difficulties students have in stoichiometry problem-solving.