Document And Entity Information - shares	9 Months Ended
	Sep. 26, 2025	Nov. 07, 2025
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 26, 2025
Document Transition Report	false
Entity File Number	001-35803
Entity Registrant Name	Mallinckrodt plc
Entity Incorporation, State or Country Code	L2
Entity Tax Identification Number	98-1088325
Entity Address, Address Line One	College Business & Technology Park
Entity Address, Address Line Two	Cruiserath
Entity Address, Address Line Three	Blanchardstown
Entity Address, City or Town	Dublin
Entity Address, Postal Zip Code	15
Entity Address, Country	IE
Country Region	353
City Area Code	1
Local Phone Number	696 0000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Bankruptcy Proceedings, Reporting Current	true
Entity Common Stock, Shares Outstanding		39,526,162
Entity Central Index Key	0001567892
Current Fiscal Year End Date	--12-26
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q3
Amendment Flag	false