Quarterly report pursuant to Section 13 or 15(d)

Document And Entity Information

Document And Entity Information - shares
6 Months Ended
Jun. 30, 2021
Aug. 03, 2021
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 Q2  
Document Fiscal Year Focus 2021  
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2021  
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  
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  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Small Business true  
Entity Filer Category Non-accelerated Filer  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Entity Shell Company false  
Title of 12(b) Security Common Stock, par value $0.001 per share  
Trading Symbol MBRX  
Security Exchange Name NASDAQ  
Entity Common Stock, Shares Outstanding   28,552,213