diff --git a/site/source/actions/companyStatusActions.ts b/site/source/actions/companyStatusActions.ts
index e6028f6d8..30d72b115 100644
--- a/site/source/actions/companyStatusActions.ts
+++ b/site/source/actions/companyStatusActions.ts
@@ -78,7 +78,7 @@ export const resetCompanyStatusChoice = (
 export const useSetEntreprise = () => {
 	const dispatch = useDispatch()
 
-	return (entreprise: FabriqueSocialEntreprise) => {
+	return (entreprise: FabriqueSocialEntreprise | null) => {
 		if (entreprise === null) {
 			return
 		}
diff --git a/site/source/api/sirene.ts b/site/source/api/sirene.ts
index a7618f592..d974cf54d 100644
--- a/site/source/api/sirene.ts
+++ b/site/source/api/sirene.ts
@@ -1,7 +1,11 @@
+import { FabriqueSocialEntreprise } from './fabrique-social'
+
 const isSIREN = (input: string) => /^[\s]*([\d][\s]*){9}$/.exec(input)
 const isSIRET = (input: string) => /^[\s]*([\d][\s]*){14}$/.exec(input)
 
-export async function fetchCompanyDetails(siren: string) {
+export async function fetchCompanyDetails(
+	siren: string
+): Promise<FabriqueSocialEntreprise | null> {
 	// Le paramètre `statut_diffusion` filtre les SIREN non diffusibles, cf.
 	// https://github.com/betagouv/mon-entreprise/issues/1399#issuecomment-770736525
 	const response = await fetch(
@@ -15,7 +19,7 @@ export async function fetchCompanyDetails(siren: string) {
 	}
 	const json = await response.json()
 
-	return json.unite_legale
+	return json.unite_legale as FabriqueSocialEntreprise
 }
 
 export async function searchDenominationOrSiren(value: string) {
diff --git a/site/source/design-system/field/SearchField.tsx b/site/source/design-system/field/SearchField.tsx
index 17ee1a857..2dbb74947 100644
--- a/site/source/design-system/field/SearchField.tsx
+++ b/site/source/design-system/field/SearchField.tsx
@@ -1,3 +1,5 @@
+import { Loader } from '@/design-system/icons/Loader'
+import { SearchIcon } from '@/design-system/icons/SearchIcon'
 import { useButton } from '@react-aria/button'
 import { useSearchField } from '@react-aria/searchfield'
 import {
@@ -5,9 +7,7 @@ import {
 	useSearchFieldState,
 } from '@react-stately/searchfield'
 import { AriaSearchFieldProps } from '@react-types/searchfield'
-import { Loader } from '@/design-system/icons/Loader'
-import { SearchIcon } from '@/design-system/icons/SearchIcon'
-import { InputHTMLAttributes, useRef } from 'react'
+import { useRef } from 'react'
 import styled, { css } from 'styled-components'
 import {
 	StyledContainer,
diff --git a/site/source/pages/Landing/SearchOrCreate.tsx b/site/source/pages/Landing/SearchOrCreate.tsx
index 9f940ba5b..ba8dc067c 100644
--- a/site/source/pages/Landing/SearchOrCreate.tsx
+++ b/site/source/pages/Landing/SearchOrCreate.tsx
@@ -1,20 +1,22 @@
 import { resetCompany } from '@/actions/companyActions'
 import { useSetEntreprise } from '@/actions/companyStatusActions'
-import { FabriqueSocialEntreprise } from '@/api/fabrique-social'
+import {
+	FabriqueSocialEntreprise,
+	searchDenominationOrSiren,
+} from '@/api/fabrique-social'
 import { CompanyDetails } from '@/components/company/Details'
 import { CompanySearchField } from '@/components/company/SearchField'
-import Value from '@/components/EngineValue'
 import Emoji from '@/components/utils/Emoji'
 import { useEngine } from '@/components/utils/EngineContext'
 import { SitePathsContext } from '@/components/utils/SitePathsContext'
-import { Message } from '@/design-system'
 import AnswerGroup from '@/design-system/answer-group'
 import { Button } from '@/design-system/buttons'
 import { Spacing } from '@/design-system/layout'
-import { H3, H4 } from '@/design-system/typography/heading'
+import { H3 } from '@/design-system/typography/heading'
 import { RootState } from '@/reducers/rootReducer'
+import { getCookieValue } from '@/storage/readCookie'
 import { Grid } from '@mui/material'
-import { useCallback, useContext } from 'react'
+import { useCallback, useContext, useEffect } from 'react'
 import { Trans } from 'react-i18next'
 import { useDispatch, useSelector } from 'react-redux'
 import { useHistory } from 'react-router-dom'
@@ -25,6 +27,7 @@ export default function SearchOrCreate() {
 		(state: RootState) => state.choixStatutJuridique.companyStatusChoice
 	)
 	const companySIREN = useEngine().evaluate('entreprise . SIREN').nodeValue
+	useSetEntrepriseFromUrssafConnection()
 	const handleCompanySubmit = useHandleCompanySubmit()
 	const dispatch = useDispatch()
 
@@ -87,3 +90,41 @@ function useHandleCompanySubmit() {
 
 	return handleCompanySubmit
 }
+
+function useSetEntrepriseFromUrssafConnection() {
+	const setEntreprise = useSetEntreprise()
+	const siret = siretFromUrssafFrConnection()
+	const companySIREN = useEngine().evaluate('entreprise . SIREN').nodeValue
+	useEffect(() => {
+		if (siret && !companySIREN) {
+			searchDenominationOrSiren(siret)
+				.then((results) => {
+					if (results?.length !== 1) {
+						return
+					}
+					setEntreprise(results[0])
+				})
+				.catch((err) => {
+					console.log(err)
+					console.log(`Could not fetch company details for ${siret}`)
+				})
+		}
+	}, [siret, companySIREN])
+}
+
+// We can read cookies set on the urssaf.fr domain, which contain informations
+// such as the SIRET number. The cookie format could change at any time so we
+// wrap its read access in a `try / catch`.
+function siretFromUrssafFrConnection(): string | null {
+	try {
+		// Note: The `ctxUrssaf` contains more informations, but currently we only
+		// need to retreive the SIRET which is slightly more easy to read from the
+		// `EnLigne` cookie.
+		const cookieValue = decodeURIComponent(getCookieValue('EnLigne'))
+		const siret = cookieValue.match('siret=([0-9]{14})')?.pop()
+
+		return siret ?? null
+	} catch {
+		return null
+	}
+}
diff --git a/site/source/storage/readCookie.ts b/site/source/storage/readCookie.ts
new file mode 100644
index 000000000..82d27997e
--- /dev/null
+++ b/site/source/storage/readCookie.ts
@@ -0,0 +1,8 @@
+// From https://stackoverflow.com/a/25490531
+export function getCookieValue(cookieName: string) {
+	return (
+		document.cookie
+			.match('(^|;)\\s*' + cookieName + '\\s*=\\s*([^;]+)')
+			?.pop() || ''
+	)
+}