Annual report pursuant to Section 13 and 15(d)

Document And Entity Information

Document And Entity Information - USD ($)
12 Months Ended
Dec. 31, 2020
Mar. 11, 2021
Jun. 30, 2020
Document Information [Line Items]      
Entity Central Index Key 0001659617    
Entity Registrant Name Moleculin Biotech, Inc.    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2020    
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2020    
Document Transition Report false    
Entity File Number 001-37758    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 47-4671997    
Entity Address, Address Line One 5300 Memorial Drive, Suite 950    
Entity Address, City or Town Houston    
Entity Address, State or Province TX    
Entity Address, Postal Zip Code 77007    
City Area Code 713    
Local Phone Number 300-5160    
Title of 12(b) Security Common Stock, par value $0.001 per share    
Trading Symbol MBRX    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company true    
Entity Ex Transition Period true    
Entity Shell Company false    
Entity Public Float     $ 52,000,000
Entity Common Stock, Shares Outstanding   28,444,425