Consolidated Statements of Stockholders’ Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	Total Stockholders’ Equity (Deficit) attributable to Millendo Therapeutics, Inc.	Total Equity Attributable to Noncontrolling Interests
Balance at beginning (in shares) at Dec. 31, 2018		13,357,999
Balance at beginning at Dec. 31, 2018	$ 73,122	$ 13	$ 234,876	$ (164,086)	$ 148	$ 70,951	$ 2,171
Stockholder's equity
Exercise of stock options (in shares)		45,947
Exercise of stock options	166		166			166
Exercise/forfeiture of BSPCE warrants (in shares)		8,112
Exercise/forfeiture of BSPCE warrants	48		160			160	(112)
Stock-based compensation expense	1,934		1,934			1,934
Foreign currency translation adjustment	(8)				(8)	(8)
Net loss	(20,237)			(20,237)		(20,237)
Balance at end (in shares) at Jun. 30, 2019		13,412,058
Balance at end at Jun. 30, 2019	55,025	$ 13	237,136	(184,323)	140	52,966	2,059
Balance at beginning (in shares) at Mar. 31, 2019		13,357,999
Balance at beginning at Mar. 31, 2019	63,686	$ 13	235,815	(174,452)	139	61,515	2,171
Stockholder's equity
Exercise of stock options (in shares)		45,947
Exercise of stock options	166		166			166
Exercise/forfeiture of BSPCE warrants (in shares)		8,112
Exercise/forfeiture of BSPCE warrants	48		160			160	(112)
Stock-based compensation expense	995		995			995
Foreign currency translation adjustment	1				1	1
Net loss	(9,871)			(9,871)		(9,871)
Balance at end (in shares) at Jun. 30, 2019		13,412,058
Balance at end at Jun. 30, 2019	55,025	$ 13	237,136	(184,323)	140	52,966	2,059
Balance at beginning (in shares) at Dec. 31, 2019		18,266,545
Balance at beginning at Dec. 31, 2019	59,871	$ 18	267,018	(208,654)	165	58,547	1,324
Stockholder's equity
Issuance of common stock, net of issuance costs (in shares)		719,400
Issuance of common stock, net of issuance costs	$ 5,650	$ 1	5,649			5,650
Exercise of stock options (in shares)	1,449	1,449
Exercise of stock options	$ 2		2			2
Exercise/forfeiture of BSPCE warrants (in shares)		12,307
Exercise/forfeiture of BSPCE warrants	78		734			734	(656)
Stock-based compensation expense	2,060		2,060			2,060
Foreign currency translation adjustment	(47)				(47)	(47)
Net loss	(22,670)			(22,670)		(22,670)
Balance at end (in shares) at Jun. 30, 2020		18,999,701
Balance at end at Jun. 30, 2020	44,944	$ 19	275,463	(231,324)	118	44,276	668
Balance at beginning (in shares) at Mar. 31, 2020		18,998,252
Balance at beginning at Mar. 31, 2020	54,639	$ 19	274,340	(220,652)	123	53,830	809
Stockholder's equity
Exercise of stock options (in shares)		1,449
Exercise of stock options	2		2			2
Exercise/forfeiture of BSPCE warrants	0		141			141	(141)
Stock-based compensation expense	980		980			980
Foreign currency translation adjustment	(5)				(5)	(5)
Net loss	(10,672)			(10,672)		(10,672)
Balance at end (in shares) at Jun. 30, 2020		18,999,701
Balance at end at Jun. 30, 2020	$ 44,944	$ 19	$ 275,463	$ (231,324)	$ 118	$ 44,276	$ 668