diff --git a/.changeset/proud-lamps-marry.md b/.changeset/proud-lamps-marry.md
new file mode 100644
index 00000000000..35a587ef6d7
--- /dev/null
+++ b/.changeset/proud-lamps-marry.md
@@ -0,0 +1,5 @@
+---
+"@primer/components": patch
+---
+
+Migrate `Breadcrumb` to TypeScript
diff --git a/src/Breadcrumb.js b/src/Breadcrumb.tsx
similarity index 61%
rename from src/Breadcrumb.js
rename to src/Breadcrumb.tsx
index 8c6d0263d32..0edbf8a80e2 100644
--- a/src/Breadcrumb.js
+++ b/src/Breadcrumb.tsx
@@ -1,11 +1,13 @@
-import React from 'react'
-import PropTypes from 'prop-types'
 import classnames from 'classnames'
+import * as History from 'history'
+import PropTypes from 'prop-types'
+import React from 'react'
 import styled from 'styled-components'
-import sx from './sx'
-import {COMMON, FLEX, get} from './constants'
-import theme from './theme'
 import Box from './Box'
+import {COMMON, FLEX, get, SystemCommonProps, SystemFlexProps} from './constants'
+import sx, {SxProp} from './sx'
+import theme from './theme'
+import {ComponentProps} from './utils/types'
 
 const SELECTED_CLASS = 'selected'
 
@@ -30,31 +32,39 @@ const Wrapper = styled.li`
   }
 `
 
-const BreadcrumbBase = ({className, children, theme, ...rest}) => {
+const BreadcrumbBase = styled.nav<SystemFlexProps & SystemCommonProps & SxProp>`
+  display: flex;
+  justify-content: space-between;
+  ${COMMON};
+  ${FLEX};
+  ${sx};
+`
+
+export type BreadcrumbProps = ComponentProps<typeof BreadcrumbBase>
+
+function Breadcrumb({className, children, theme, ...rest}: React.PropsWithChildren<BreadcrumbProps>) {
   const classes = classnames(className, 'Breadcrumb')
   const wrappedChildren = React.Children.map(children, child => <Wrapper theme={theme}>{child}</Wrapper>)
   return (
-    <nav className={classes} aria-label="breadcrumb" {...rest}>
+    <BreadcrumbBase className={classes} aria-label="breadcrumb" theme={theme} {...rest}>
       <Box as="ol" my={0} pl={0}>
         {wrappedChildren}
       </Box>
-    </nav>
+    </BreadcrumbBase>
   )
 }
 
-const Breadcrumb = styled(BreadcrumbBase)`
-  display: flex;
-  justify-content: space-between;
-  ${COMMON};
-  ${FLEX};
-  ${sx};
-`
+type StyledBreadcrumbItemProps = {
+  to?: History.LocationDescriptor
+  selected?: boolean
+} & SystemCommonProps &
+  SxProp
 
-Breadcrumb.Item = styled.a.attrs(props => ({
+const BreadcrumbItem = styled.a.attrs<StyledBreadcrumbItemProps>(props => ({
   activeClassName: typeof props.to === 'string' ? 'selected' : '',
   className: classnames(props.selected && SELECTED_CLASS, props.className),
   'aria-current': props.selected ? 'page' : null
-}))`
+}))<StyledBreadcrumbItemProps>`
   color: ${get('colors.blue.5')};
   display: inline-block;
   font-size: ${get('fontSizes.1')};
@@ -81,18 +91,18 @@ Breadcrumb.propTypes = {
 
 Breadcrumb.displayName = 'Breadcrumb'
 
-Breadcrumb.Item.defaultProps = {
+BreadcrumbItem.defaultProps = {
   theme
 }
 
-Breadcrumb.Item.propTypes = {
-  as: PropTypes.oneOfType([PropTypes.string, PropTypes.elementType]),
+BreadcrumbItem.propTypes = {
   href: PropTypes.string,
   selected: PropTypes.bool,
   ...sx.propTypes,
   ...COMMON.propTypes
 }
 
-Breadcrumb.Item.displayName = 'Breadcrumb.Item'
+BreadcrumbItem.displayName = 'Breadcrumb.Item'
 
-export default Breadcrumb
+export type BreadcrumbItemProps = ComponentProps<typeof BreadcrumbItem>
+export default Object.assign(Breadcrumb, {Item: BreadcrumbItem})
diff --git a/src/__tests__/Breadcrumb.js b/src/__tests__/Breadcrumb.tsx
similarity index 100%
rename from src/__tests__/Breadcrumb.js
rename to src/__tests__/Breadcrumb.tsx
diff --git a/src/__tests__/BreadcrumbItem.js b/src/__tests__/BreadcrumbItem.tsx
similarity index 70%
rename from src/__tests__/BreadcrumbItem.js
rename to src/__tests__/BreadcrumbItem.tsx
index 76bbfa62221..0630d5efb70 100644
--- a/src/__tests__/BreadcrumbItem.js
+++ b/src/__tests__/BreadcrumbItem.tsx
@@ -1,10 +1,10 @@
+import {cleanup, render as HTMLRender} from '@testing-library/react'
+import 'babel-polyfill'
+import {axe, toHaveNoViolations} from 'jest-axe'
 import React from 'react'
 import {Breadcrumb} from '..'
-import {render, behavesAsComponent} from '../utils/testing'
 import {COMMON} from '../constants'
-import {render as HTMLRender, cleanup} from '@testing-library/react'
-import {axe, toHaveNoViolations} from 'jest-axe'
-import 'babel-polyfill'
+import {behavesAsComponent, render} from '../utils/testing'
 expect.extend(toHaveNoViolations)
 
 describe('Breadcrumb.Item', () => {
@@ -26,9 +26,7 @@ describe('Breadcrumb.Item', () => {
   })
 
   it('adds activeClassName={SELECTED_CLASS} when it gets a "to" prop', () => {
-    const Mock = jest.fn(() => <div />)
-    render(<Breadcrumb.Item as={Mock} to="#" />)
-    expect(Mock.mock.calls[0][0].to).toEqual('#')
-    expect(Mock.mock.calls[0][0].activeClassName).toEqual('selected')
+    const Link = ({theme, ...props}: any) => <div {...props} />
+    expect(render(<Breadcrumb.Item as={Link} to="#" />)).toMatchSnapshot()
   })
 })
diff --git a/src/__tests__/__snapshots__/Breadcrumb.js.snap b/src/__tests__/__snapshots__/Breadcrumb.tsx.snap
similarity index 100%
rename from src/__tests__/__snapshots__/Breadcrumb.js.snap
rename to src/__tests__/__snapshots__/Breadcrumb.tsx.snap
diff --git a/src/__tests__/__snapshots__/BreadcrumbItem.js.snap b/src/__tests__/__snapshots__/BreadcrumbItem.tsx.snap
similarity index 64%
rename from src/__tests__/__snapshots__/BreadcrumbItem.js.snap
rename to src/__tests__/__snapshots__/BreadcrumbItem.tsx.snap
index c25b60f5693..467b10d0148 100644
--- a/src/__tests__/__snapshots__/BreadcrumbItem.js.snap
+++ b/src/__tests__/__snapshots__/BreadcrumbItem.tsx.snap
@@ -1,5 +1,32 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`Breadcrumb.Item adds activeClassName={SELECTED_CLASS} when it gets a "to" prop 1`] = `
+.c0 {
+  color: #0366d6;
+  display: inline-block;
+  font-size: 14px;
+  -webkit-text-decoration: none;
+  text-decoration: none;
+}
+
+.c0:hover {
+  -webkit-text-decoration: underline;
+  text-decoration: underline;
+}
+
+.c0.selected {
+  color: #444d56;
+  pointer-events: none;
+}
+
+<div
+  activeClassName="selected"
+  aria-current={null}
+  className="c0"
+  to="#"
+/>
+`;
+
 exports[`Breadcrumb.Item renders consistently 1`] = `
 .c0 {
   color: #0366d6;