The International Cricket Council will give West Indies and Zimbabwe financial support to help their national teams.
The WICB will receive £2m over three years as part of the Targeted Assistance and Performance Programme (TAPP) agreement, with Zimbabwe's board receiving half that amount over the same period.
The Windies were the surprise winners of the ICC World Twenty20 in Sri Lanka last year, but their Test team has been sliding down the rankings in recent years.
Only New Zealand and Bangladesh are below them in the official ICC rankings, with Zimbabwe currently unranked as they have played insufficient matches.
ICC chief executive David Richardson said: "It is very important to the long term prosperity of international cricket that we have competitive teams at the highest level and both the West Indies and Zimbabwe have been very clear in identifying the factors that will support improved performance.
"The TAPP agreements provide an opportunity for both members to increase their investment in high performance and we look forward to witnessing the impact of these programmes."
The agreements with both nations follows similar targeted performance support for Ireland, Holland and Scotland, while details of New Zealand's programme are being finalised.