The last two decades have facilitated considerable progress in understanding the impacts of climate change on crop sensitivity and production, however very few of these studies have incorporated the activity of herbivorous insect pests into their assessments of potential yield losses. In Ireland, the grain aphid (Sitobion avenae) is the most commonly encountered aphid pest in cereal crops. This pest confers significant decreases in crop yields owing to its mechanical feeding damage, as well as its ability to vector plant viruses. Despite the damage potential, climate-induced changes to aphid populations have not been considered in the context of Irish agricultural production. The work presented here integrates biological data from various studies to inform the development of a simulation model to describe the population dynamics of S. avenae for multiple locations in Ireland in response to climate change. The simulation model (SAV4) describes the compartmentalised life cycle history of S. avenae in response to temperature, incorporating immigration, reproduction, survival, development and morph determination, facilitating the calculation of annual phenological and quantitative aphid metrics. The model was evaluated using observations describing aphid immigration, timing and size of populations in order to ensure that it was fit for purpose. Projected temperature data derived from three Global Climate Models (GCMs) and two green house gas projection pathways, were used to drive the aphid simulation model for eleven locations in Ireland. Reported findings include increases in both aphid abundance and voltinism, as well as advanced phenology across all sites for Ireland. The extent of modelled change was found to differ spatially, with current areas of spring barley cultivation experiencing some of the most significant alterations to S. avenae’s dynamics over time. These findings highlight potential increases in pest risk under climate change in Ireland, emphasising the need for monitoring programmes in conjunction with an Integrated Pest Management (IPM) approach in order to ensure crop resilience in the future. This work constitutes the first explicit incorporation of pest dynamics into climate change projections for the Republic of Ireland, as well as providing a novel pest model for use in pest risk analysis. More broadly, the findings presented here contribute to a growing body of work concerning the mediating effects of climate-induced pest activities in food security.