BackgroundThe COVID-19 Vaccine Introduction and deployment Costing (CVIC) tool was developed to assist countries to estimate incremental financial costs to roll out COVID-19 vaccines. This article describes the purposes, assumptions and methods used in the CVIC tool and presents the estimated financial costs of delivering COVID-19 vaccines in the Lao People’s Democratic Republic (Lao PDR).MethodsFrom March to September 2021, a multidisciplinary team in Lao PDR was involved in the costing exercise of the National Deployment and Vaccination Plan for COVID-19 vaccines to develop potential scenarios and gather inputs using the CVIC tool. Financial costs of introducing COVID-19 vaccines for 3 years from 2021 to 2023 were projected from the government perspective. All costs were collected in 2021 Lao Kip and presented in United States dollar.ResultsFrom 2021 to 2023, the financial cost required to vaccinate all adults in Lao PDR with primary series of COVID-19 vaccines (1 dose for Ad26.COV2.S (recombinant) vaccine and 2 doses for the other vaccine products) is estimated to be US$6.44 million (excluding vaccine costs) and additionally US$1.44 million and US$1.62 million to include teenagers and children, respectively. These translate to financial costs of US$0.79–0.81 per dose, which decrease to US$0.6 when two boosters are introduced to the population. Capital and operational cold-chain costs contributed 15–34% and 15–24% of the total costs in all scenarios, respectively. 17–26% went to data management, monitoring and evaluation, and oversight, and 13–22% to vaccine delivery.ConclusionsWith the CVIC tool, costs of five scenarios were estimated with different target population and booster dose use. These facilitated Lao PDR to refine their strategic planning for COVID-19 vaccine rollout and to decide on the level of external resources needed to mobilize and support outreach services. The results may further inform inputs in cost-effectiveness or cost–benefit analyses and potentially be applied and adjusted in similar low- and middle-income settings.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12916-023-02944-1.