Document And Entity Information - shares	6 Months Ended
	Jun. 28, 2019	Aug. 02, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Entity File Number	001-35803
Security Exchange Name	NYSE
Entity Registrant Name	Mallinckrodt plc
Entity Incorporation, State or Country Code	L2
Entity Tax Identification Number	98-1088325
Entity Address, Address Line One	3 Lotus Park, The Causeway
Entity Address, City or Town	Staines-Upon-Thames
Entity Address, Postal Zip Code	TW18 3AG
Entity Address, Country	GB
City Area Code	017
Local Phone Number	8463 6700
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Central Index Key	0001567892
Trading Symbol	MNK
Title of 12(b) Security	Ordinary shares, par value $0.20 per share
Current Fiscal Year End Date	--12-27
Entity Filer Category	Large Accelerated Filer
Document Period End Date	Jun. 28, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Ordinary Shares Outstanding		84,008,556
Entity Emerging Growth Company	false
Entity Small Business	false