The move offers both companies an answer to Amazon's giant ecommerce business, which poses a growing threat both to physical retailers and parts of Google's business that serve product search.
Walmart has become the largest retailer to offer products to consumers who shop on Google Express, following similar deals with Costco and Target.
Google Express users will be able to order products from Walmart through Google Home, the search firm's answer to Amazon's Alexa-powered Echo. Google launched voice shopping from Home with companies like Costco and Walgreens earlier this year to match Alexa's shopping capabilities.
Google Express is integrated with Walmart's Easy Reorder, allowing consumers to use Google Home to create a shopping list of items they've previously purchased. Walmart launched Easy Reorder this year to help customers build online lists of goods they'd purchased in store.
It intends to offer personalized recommendations using Easy Reorder data. Once customers link their Express and Walmart accounts, Google Assistant will be able to provide the same recommendations. Walmart's move to voice shopping comes amid Amazon's push into the grocery market with its $13.7bn Whole Foods acquisition.
Walmart next year will launch voice shopping for fresh groceries, which customers can pick up from any of its 4,700 stores across the US.
The alliance with Google Express follows Walmart's April launch of Pickup Discount, offering its customers a discount for select goods ordered online and free two-day shipping for orders over $35.
Google has also dropped the $10 a month or $95 a year membership fee for Express and is now offering free delivery so long as an order meets each store's minimum, which is usually between $25 to $35. Orders less than the minimum cost $4.99.
The new voice shopping option for Walmart will launch in late September. Customers will initially be able to order goods from Walmart via Home. However, Brian Elliot, GM at Google Express, told TechCrunch it will eventually expand to Google Assistant and voice interactions on other devices.