Quarterly report pursuant to Section 13 or 15(d)


Cover - shares
6 Months Ended
Jun. 30, 2020
Aug. 07, 2020
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2020  
Document Transition Report false  
Entity File Number 001-37758  
Entity Registrant Name MOLECULIN BIOTECH, INC.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 47-4671997  
Entity Address, Street Address 5300 Memorial Drive,  
Entity Address, Suite Suite 950  
Entity Address, City Houston  
Entity Address, State 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 Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Entity Shell Company false  
Title of each class Common Stock, par value $0.001 per share  
Trading Symbol MBRX  
Name of each exchange on which registered NASDAQ  
Entity Common Stock, Shares Outstanding (in shares)   61,704,290
Document Fiscal Year Focus 2020  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Central Index Key 0001659617