Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 10, 2021
Document And Entity Information
Entity Central Index Key	0000065596
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2021
Entity File Number	0-5703
Entity Registrant Name	Siebert Financial Corp
Entity Incorporation State or Country Code	NY
Entity Tax Identification Number	11-1796714
Entity Address, Address Line One	120 Wall Street
Entity Address, City or Town	NY
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10005
City Area Code	212
Local Phone Number	644-2400
Title of 12(b) Security	Common Stock - $0.01 par value
Trading Symbol	SIEB
Name of Exchange on which Security is Registered	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		31,283,364